Subtract to Unlock the Chest Game
Kids see a three-digit subtraction stacked on the lock — like 735 minus 497 — and type each digit of the difference into the keypad to unlock the chest. It's the same way Cuemath tutors anchor regrouping in live 1:1 classes.
Treasure Den
Grade 3
5 min · 3 rounds
Used in Cuemath 1:1 classes
About the game
Subtract to Unlock the Chest is a free online math game for Grade 3 students learning three-digit subtraction with regrouping. Each chest shows a vertical subtraction — say, 735 minus 497 — stacked above three empty digit boxes. The student works out the difference (which usually requires regrouping across columns) and types each digit into the boxes; entering the correct difference clicks open one of the chest’s two locks. Three chests, two locks each — six subtractions in all — and a surprise reveal once every chest is open. Across the run, students build the core insight that regrouping isn’t a special trick: it’s a way of borrowing ten from the next column when the top digit is too small to subtract from.
From the classroom
How Cuemath Tutors Use This Game
Tutors use this when a student can subtract two-digit numbers comfortably but starts losing accuracy as soon as regrouping enters the picture. Treasure Den forces the regrouping question to the front: a problem like 735 - 497 has it in two columns at once, and the student can't type the right answer without working through both. The chest lock is the discipline — it accepts the right three digits, nothing else.
Once a student has unlocked a few chests, the columns stop feeling separate and start feeling like a system. Tutors often pause before the student types and ask 'which columns will need borrowing here?' so the regrouping step is named upfront, not stumbled through halfway.
Often paired with
Two-digit subtraction with regrouping before, multi-digit subtraction and place-value problems after.
What students said
Students worked the columns in their heads — pointing at the ones digit, muttering 'borrow', then typing each digit of the answer in turn and watching the lock click open.
Grade 3 classroom feedback
Collected across 70+ live 1:1 classes
Cuemath 1:1 classes
A Cuemath tutor can do what a game can’t — diagnose exactly where your child gets stuck on arithmetic operations, and sequence what comes next.
What Your Child Practices
Four dimensions from the Cuemath FUAR taxonomy — Fluency, Understanding, Application, Reasoning — applied to this game.
Fluency
Fluency in three-digit subtraction — including problems where regrouping is required across multiple columns.
Understanding
Understanding that regrouping is borrowing ten from the next column over: it doesn’t change the number being subtracted from, only the way its digits are written.
Application
Application of regrouping reasoning across six subtractions — three chests, two locks each — varied to bring out different regrouping patterns.
Reasoning
Reasoning about why borrowing in one column changes the digit in the next — and why every wrong-looking column in 735 - 497 still adds up to the right total once regrouping is accounted for.
You might also like
More Arithmetic Games
View All Games →
Grade 2 · Arithmetic Operations
The Missing Number Locker
Find the missing addend and crack open each safe.
Grade 4 · Arithmetic Operations
Divide the Candies
Type the quotient and watch the candies split into equal groups.
Grade 4 · Arithmetic Operations
Multiply to Harvest
Type the product of single-digit multiplication and harvest the orchard.
Curriculum
Explore the Full Grade 3 Math Curriculum
See All Topics →
Games Build Curiosity. Cuemath Builds Mastery.
Watch how a Cuemath 1-on-1 online math class works — and why
400,000+ parents
chose it over other tutoring options.
Book a Free Trial Class
Book
a
Free
Trial
Class
a
Free
Trial
Class
Manan Khurma
- Cuemath founder
- IIT Delhi Alumnus
- 10K+ Kids Taught
- 20+ Years of Teaching
Games Build Curiosity. Cuemath Builds Mastery.
Watch how a Cuemath 1-on-1 online math class works — and why
400,000+ parents
chose it over other tutoring options.
Manan Khurma
- Cuemath founder
- IIT Delhi Alumnus
- 10K+ Kids Taught
- 20+ Years of Teaching
Book a Free Trial Class
Book
a
Free
Trial
Class
a
Free
Trial
Class
Trusted by Parents
Loved by Students
Loved by Students
4.9+
200K+
Students
80+
Countries
200K+
Students
4.9+
80+
Countries
Exceptional Guidance
"Ms. Shalini Kumar is the best of the best—very experienced and always working hard with my daughter to help her achieve great results in math. We continue booking with her every year."
LH
Linet Haratunian
🇺🇸
Dedicated Math Mentor
"Ms SURANA has real enthusiasm and energy to teach. My kids improved their math skills drastically with her. Thanks Ms Priya."
ÜA
Ümit Aykut
🇺🇸
Motivation That Works
"Reena is an amazing teacher who builds motivation gently and effectively. Our son looks forward to every session. Cuemath has deepened his understanding and let him explore topics he loves."
J
Jen
🇺🇸
Caring, Clear Support
"As a parent, I feel valued and supported by Mrs. Puduru Sandeepa. She involves me, always communicates clearly, and creates a caring environment that improves my daughter's understanding."
E
Eliza
🇺🇸
Confidence in Math
"My daughter has made major academic improvements since joining Cuemath. She's more confident because Ms. Supriya teaches using her school textbooks. Enrolling her in Cuemath was a great decision!"
MO
Myra Olarte
🇺🇸
Math Support for ADHD
"I'm so grateful for the amazing support Ms. Mehak has given my son with ADHD. Her patience and creative teaching have built his confidence. He looks forward to math and enjoys learning!"
S
Shital
🇺🇸
Math Made Enjoyable
"Ms. Supriya has been teaching my daughters for 3 years. She tailors lessons patiently, builds confidence, and skills. My girls actually enjoy learning math with her, which says a lot!"
P
Payal
🇺🇸
Love for Math Lessons
"Our son looks forward to his math lessons with Ms. Sonal Kesal. She is incredibly patient, explains concepts clearly, keeps him engaged. He progressed to 5th grade math mid-4th grade."
R
Radhika
🇺🇸
Ahead in Math
"My daughter has been with Cuemath for 2+ years. With tutor Anjali and engaging worksheets, she's made tremendous progress and can confidently solve 2nd-grade math in 1st grade."
KC
Karpukkarasi Chandrasekar
🇺🇸
Math Skills Improved
"My son has been with Cuemath for 5 years, from 1st-6th grade. I've seen a huge improvement in his confidence and problem-solving skills. He now approaches math with excitement, not fear."
RS
Ravikumar Sidda
🇺🇸
Wonderful Math Teacher
"My 3rd-grade son has improved greatly, and his love for math puzzles has grown tremendously after joining Cuemath. Ms. Atluri Ratna's expertise and engaging teaching make math truly enjoyable."
PD
Prasanna Devi
🇺🇸
Love for Math
"Our 4th grader loves math thanks to Rashmi Mam. Her patient, fun, and encouraging teaching has boosted confidence, focus, and test performance—making every session enjoyable."
SJ
Santhosh Jha
🇺🇸
Awesome Math Teacher
"Thanks to Abanti Mitra Mam. She's been a wonderful teacher for our 7th-grade daughter for 2.5 years. Patient, explains concepts well, adjusts timings, and gave extra sessions before exams."
JV
Jahnavi Vutharkar
🇺🇸
Gaining Confidence
"My child in 7th grade has gained confidence in math reasoning with Cuemath teacher Payal Agrawal. She explains concepts clearly and tailors her teaching to my child."
RS
Rekha Silwal
🇺🇸
Math Feels Easy
"My son started Cuemath in 2nd grade and still loves it in 5th! Thanks to Ms. Vinita's creative, fun teaching, math feels easy and exciting. He looks forward to every Cuemath class!"
SD
Shyam Deshmukh
🇺🇸
Exceptional Guidance
"Ms. Shalini Kumar is the best of the best—very experienced and always working hard with my daughter to help her achieve great results in math. We continue booking with her every year."
LH
Linet Haratunian
🇺🇸
Dedicated Math Mentor
"Ms SURANA has real enthusiasm and energy to teach. My kids improved their math skills drastically with her. Thanks Ms Priya."
ÜA
Ümit Aykut
🇺🇸
Motivation That Works
"Reena is an amazing teacher who builds motivation gently and effectively. Our son looks forward to every session. Cuemath has deepened his understanding and let him explore topics he loves."
J
Jen
🇺🇸
Caring, Clear Support
"As a parent, I feel valued and supported by Mrs. Puduru Sandeepa. She involves me, always communicates clearly, and creates a caring environment that improves my daughter's understanding."
E
Eliza
🇺🇸
Confidence in Math
"My daughter has made major academic improvements since joining Cuemath. She's more confident because Ms. Supriya teaches using her school textbooks. Enrolling her in Cuemath was a great decision!"
MO
Myra Olarte
🇺🇸
Math Support for ADHD
"I'm so grateful for the amazing support Ms. Mehak has given my son with ADHD. Her patience and creative teaching have built his confidence. He looks forward to math and enjoys learning!"
S
Shital
🇺🇸
Math Made Enjoyable
"Ms. Supriya has been teaching my daughters for 3 years. She tailors lessons patiently, builds confidence, and skills. My girls actually enjoy learning math with her, which says a lot!"
P
Payal
🇺🇸
Love for Math Lessons
"Our son looks forward to his math lessons with Ms. Sonal Kesal. She is incredibly patient, explains concepts clearly, keeps him engaged. He progressed to 5th grade math mid-4th grade."
R
Radhika
🇺🇸
Ahead in Math
"My daughter has been with Cuemath for 2+ years. With tutor Anjali and engaging worksheets, she's made tremendous progress and can confidently solve 2nd-grade math in 1st grade."
KC
Karpukkarasi Chandrasekar
🇺🇸
Math Skills Improved
"My son has been with Cuemath for 5 years, from 1st-6th grade. I've seen a huge improvement in his confidence and problem-solving skills. He now approaches math with excitement, not fear."
RS
Ravikumar Sidda
🇺🇸
Wonderful Math Teacher
"My 3rd-grade son has improved greatly, and his love for math puzzles has grown tremendously after joining Cuemath. Ms. Atluri Ratna's expertise and engaging teaching make math truly enjoyable."
PD
Prasanna Devi
🇺🇸
Love for Math
"Our 4th grader loves math thanks to Rashmi Mam. Her patient, fun, and encouraging teaching has boosted confidence, focus, and test performance—making every session enjoyable."
SJ
Santhosh Jha
🇺🇸
Awesome Math Teacher
"Thanks to Abanti Mitra Mam. She's been a wonderful teacher for our 7th-grade daughter for 2.5 years. Patient, explains concepts well, adjusts timings, and gave extra sessions before exams."
JV
Jahnavi Vutharkar
🇺🇸
Gaining Confidence
"My child in 7th grade has gained confidence in math reasoning with Cuemath teacher Payal Agrawal. She explains concepts clearly and tailors her teaching to my child."
RS
Rekha Silwal
🇺🇸
Math Feels Easy
"My son started Cuemath in 2nd grade and still loves it in 5th! Thanks to Ms. Vinita's creative, fun teaching, math feels easy and exciting. He looks forward to every Cuemath class!"
SD
Shyam Deshmukh
🇺🇸
Exceptional Guidance
"Ms. Shalini Kumar is the best of the best—very experienced and always working hard with my daughter to help her achieve great results in math. We continue booking with her every year."
LH
Linet Haratunian
🇺🇸
Dedicated Math Mentor
"Ms SURANA has real enthusiasm and energy to teach. My kids improved their math skills drastically with her. Thanks Ms Priya."
ÜA
Ümit Aykut
🇺🇸
Motivation That Works
"Reena is an amazing teacher who builds motivation gently and effectively. Our son looks forward to every session. Cuemath has deepened his understanding and let him explore topics he loves."
J
Jen
🇺🇸
Caring, Clear Support
"As a parent, I feel valued and supported by Mrs. Puduru Sandeepa. She involves me, always communicates clearly, and creates a caring environment that improves my daughter's understanding."
E
Eliza
🇺🇸
Confidence in Math
"My daughter has made major academic improvements since joining Cuemath. She's more confident because Ms. Supriya teaches using her school textbooks. Enrolling her in Cuemath was a great decision!"
MO
Myra Olarte
🇺🇸
Math Support for ADHD
"I'm so grateful for the amazing support Ms. Mehak has given my son with ADHD. Her patience and creative teaching have built his confidence. He looks forward to math and enjoys learning!"
S
Shital
🇺🇸
Math Made Enjoyable
"Ms. Supriya has been teaching my daughters for 3 years. She tailors lessons patiently, builds confidence, and skills. My girls actually enjoy learning math with her, which says a lot!"
P
Payal
🇺🇸
Love for Math Lessons
"Our son looks forward to his math lessons with Ms. Sonal Kesal. She is incredibly patient, explains concepts clearly, keeps him engaged. He progressed to 5th grade math mid-4th grade."
R
Radhika
🇺🇸
Ahead in Math
"My daughter has been with Cuemath for 2+ years. With tutor Anjali and engaging worksheets, she's made tremendous progress and can confidently solve 2nd-grade math in 1st grade."
KC
Karpukkarasi Chandrasekar
🇺🇸
Math Skills Improved
"My son has been with Cuemath for 5 years, from 1st-6th grade. I've seen a huge improvement in his confidence and problem-solving skills. He now approaches math with excitement, not fear."
RS
Ravikumar Sidda
🇺🇸
Wonderful Math Teacher
"My 3rd-grade son has improved greatly, and his love for math puzzles has grown tremendously after joining Cuemath. Ms. Atluri Ratna's expertise and engaging teaching make math truly enjoyable."
PD
Prasanna Devi
🇺🇸
Love for Math
"Our 4th grader loves math thanks to Rashmi Mam. Her patient, fun, and encouraging teaching has boosted confidence, focus, and test performance—making every session enjoyable."
SJ
Santhosh Jha
🇺🇸
Awesome Math Teacher
"Thanks to Abanti Mitra Mam. She's been a wonderful teacher for our 7th-grade daughter for 2.5 years. Patient, explains concepts well, adjusts timings, and gave extra sessions before exams."
JV
Jahnavi Vutharkar
🇺🇸
Gaining Confidence
"My child in 7th grade has gained confidence in math reasoning with Cuemath teacher Payal Agrawal. She explains concepts clearly and tailors her teaching to my child."
RS
Rekha Silwal
🇺🇸
Math Feels Easy
"My son started Cuemath in 2nd grade and still loves it in 5th! Thanks to Ms. Vinita's creative, fun teaching, math feels easy and exciting. He looks forward to every Cuemath class!"
SD
Shyam Deshmukh
🇺🇸
We love solving doubts
What is three-digit subtraction with regrouping?
Three-digit subtraction means taking one three-digit number away from another — say, 735 - 497 — and regrouping (sometimes called “borrowing”) is the move you make when the top digit in a column is smaller than the bottom one. To compute 735 - 497, you can't just subtract column by column: in the ones, 5 is less than 7. So you borrow ten from the tens column (the 3 becomes a 2) and add it to the 5, giving 15. Now 15 - 7 = 8. The same move repeats in the tens column. The result, 238, only works because the borrowed tens are tracked correctly.
Why does regrouping work?
Because the digits in a number are just shorthand for groups of hundreds, tens, and ones. When you regroup, you're not changing the value of the number — you're changing how the digits are written. The number 735 is the same whether you read it as “7 hundreds + 3 tens + 5 ones” or “7 hundreds + 2 tens + 15 ones.” Both describe the same total. Regrouping just moves a ten from the tens column into the ones column, so the subtraction can proceed. Once a student sees regrouping as rewriting (not borrowing-as-mystery), the procedure stops feeling arbitrary and starts feeling like simple accountancy.
Does the game explain how to play?
No — the game doesn’t need one. The chest displays the subtraction problem stacked above three empty digit boxes, so the layout itself shows what to do: work out the difference, type the digits, click Unlock. Kids can start playing the moment the page loads.
How long does it take to play?
A full playthrough of all 3 chests — six subtractions in total — takes about 5 minutes. Each chest has two locks, and each lock is one three-digit subtraction; the pace is set by how long the student wants to spend on the regrouping in each problem. There's no time pressure — the chest waits.
Is the game free? Will it stay free?
Yes. Subtract to Unlock the Chest is free to play now and will remain free. It's part of Cuemath Playground — a library of games that Cuemath tutors use with paying students, made freely available as part of Cuemath's mission to make every child MathFit. No signups, no paywalls, no hidden tiers.
Are there ads or distractions in the game?
No. The game has no third-party ads, no pop-ups, no promotional interruptions, no chat, and no user-generated content. A child can play any round from start to finish with nothing on screen except the game itself.
What should my child learn after this?
Once a child can confidently subtract three-digit numbers with regrouping, the natural next steps are subtraction with even larger numbers (where regrouping may need to ripple across more columns), addition with regrouping (which uses the same place-value bookkeeping in reverse), and word problems where the student has to decide which numbers go on top. All are Grade 3–4 topics covered in other Cuemath Playground games and in the full Grade 3 math curriculum.
How is this different from Math Gym in the Cuemath app?
This game lives on Cuemath's website as part of Cuemath Playground — a free, browser-based library of concept-specific games tied to grade-level curriculum (this one is built around Grade 3 arithmetic operations). Math Gym is a separate section inside the Cuemath app, with daily strategy games, logic puzzles, and mental-math challenges — built around general mathematical fitness rather than a specific topic. Both belong to the MathFit journey, but they serve different purposes: Playground works through curriculum concepts; Math Gym builds daily practice across strategy, logic, and mental math. You don't need the app to play this game.
See More
See More
