Sindhu is 40 years old and Smita is 20 years old. How many years ago was Sindhu three times as old as Smita?

Equation helps us to model a real life situation using algebraic expressions

Answer: If Sindhu is 40 years old and Smita is 20 years old now, 10 years ago Sindhu was three times as old as Smita

Let 'z' years ago, Sindhu's age be 3 times as old as Smita's age 

We will be solving the value of z

Explanation:

Given: Sindhu's present age = 40 years

            Smita's present age = 20 years

'z' years ago,

Sindhu's age = 40 - z

Smita's age = 20 - z

According to the question, 'z' years ago

Sindhu's age = 3 times of Smita's age

=> 40 - z = 3 × (20 - z)

=> 40 - z = 60 - 3z

=> 2z = 60 - 40

=>  2z = 20

=>  z = 10

Therefore, if Sindhu is 40 years old and Smita is 20 years old now, 10 years ago Sindhu was three times as old as Smita