Young Einstein Mathematics Educational Software Contents

Activity Number 149

Heading : Estimating Subtraction

Description : Estimate an answer by using rounding to make the sum easier

Aim/Questions : Derived

Educational software theory used:

Estimating Subtraction

We can sometimes solve hard sums by estimating the answers.

To estimate you need to pick numbers that are easy to work with and are close to the numbers you are using.

For example if you needed to add 52 - 21, you could do an estimate first.

By looking at the numbers, we see that they are all very close to 10. We also know that 10 is an easy number pattern to add up.

Lets change the sum by substituting in the estimates

52 - 21  is close to

50 - 20

So we can say the sum is approximately = 30

Educational software Instruction :

1.  Work out the approximate answer to the question then type your answer into the ‘Answer Box’ provided.

2.  Press ‘Enter’ when you have finished.

Answers to +/- 4 are accepted as correct.

Module 149 These Instructions from 'Young Einstein Mathematics educational software by Maths Practice are Copyright. Copyright Maths Practice P/L 2003 ©