Time
Lessons in this chapter
About Time
Time in 4th grade adds seconds and, more importantly, treats time as a set of units to convert between, like any other measurement.
Read and Represent Time in Seconds completes the units. Seconds matter for the arithmetic that follows, since 90 seconds is one minute thirty and that conversion comes up constantly.
Convert Units of Time is the core lesson, and it is where time refuses to behave like everything else. Sixty seconds to a minute, sixty minutes to an hour, twenty-four hours to a day: none of these are powers of ten, so none of the metric shortcuts work.
Solve Real World Problems on Time combines conversion with elapsed time. A problem spanning 2 hours 45 minutes plus 1 hour 30 minutes needs the minutes added, the 75 converted to 1 hour 15, and the hours totalled, which is regrouping in base sixty.
All three lessons open as a 4th grade math worksheet in the page. Read and Represent Time in Seconds, Convert Units of Time and Solve Real World Problems on Time each set their own questions, worked one at a time and marked as you answer them. They are free to try, with no login needed for your first 3.
Frequently asked questions
Read and Represent Time in Seconds completes the units, which matters because 90 seconds being one minute thirty comes up constantly in what follows. Convert Units of Time is the core lesson, and it is where time refuses to behave like every other measurement, since sixty and twenty-four are not powers of ten. Solve Real World Problems on Time then combines conversion with elapsed time. The chapter sits in the Common Core domain Measurement and Data (4.MD).
Seconds, minutes, hours and days, and converting between them.
Because time is not base ten. Sixty seconds to a minute and sixty minutes to an hour means none of the place value shortcuts apply.
Add the minutes to get 75, convert that to 1 hour 15 minutes, then add the hours: 2 + 1 + 1, giving 4 hours 15 minutes.
Three thousand six hundred, which is 60 times 60. It is a useful fact because it shows the conversions compound.
Treating minutes as decimals, so writing 1.5 hours as 1 hour 50 minutes. It is 1 hour 30, because half of 60 is 30.