Using Reasoning in Guess and Check – A Quotient and Remainder Example

This is an interesting problem for quotient and remainder in Grade 3 Math in Focus Chapter 8 – Problem Solving, using guess and check.

The question requires students to use guess and check to find a number

1. between 40 and 60, and
2. if divided by 10 gives a remainder of 2, and
3. if divided by 8, also gives a remainder of 2.

Instead of blindly trying out all numbers between 40 and 60, we can use reasoning and our understanding of quotient and remainders to help us narrow down the choices!

From the video above, we see that out of the numbers between 40 and 60 (condition 1) there are only two numbers (42 and 52) that met condition 2, and three numbers (42, 50 and 58) that met condition 3. The answer is the only common number between these two lists, i.e. 42.

(Note: The above video came from our member’s resources for grade 3. For each grade, we solve selected challenging problems in the Math in Focus workbooks in short videos. Check out our membership program!)