Young Einstein Mathematics Educational Software Contents

Activity Number 33

Heading : Subtracting 2 Numbers - With Borrow

Description : Subtracting a 2 digit number with a borrow involved

Aim/Questions : Perform the subtraction.

Educational software theory used:

Subtracting 2 Numbers - With Borrow

You need to understand the borrow concept first. Lets look at an example.

The number 62 =

Tens              Ones

XXXXXX

XXXXXX

XXXXXX

XXXXXX

XXXXXX

XXXXXX

XXXXXX

XXXXXX

XXXXXX     X

XXXXXX     X

The number 62 is 6 groups of ten plus 2 groups of one.

But 62 can also be 5 groups of ten and 12 groups of one.

Tens              Ones

XXXXX      X

XXXXX      X

XXXXX      X

XXXXX      X

XXXXX      X

XXXXX      X

XXXXX      X

XXXXX      X

XXXXX      X

XXXXX      X

           X

           X

All we did in the second case was borrow one group of tens and put them in the ones column. You will see how this makes our subtraction easier.

When subtracting larger numbers start with the ones units first.

When you have completed the ones units then move to the next column of tens units and subtract the tens units.

Eg

 6 2

-1 5

Firstly work on the ones units

 6 2

–1 5

     ?? I can’t do this.

Lets change 62 from 6 tens and 2 ones to 5 tens and 12 ones and try again.

 5 12

-1  5

    7

Now lets work on the tens units. But remember that you borrowed one lot of tens and you have only 5 left.

 5 12

-1  5

 4  7

Therefore

 62

–15

 47

Educational software Instruction :

1.  Subtract the number and type the difference into the ‘Answer Box’ provided.

2.  Press ‘Enter’ when you have finished.

Click on the ‘Wording’ check box if you want the sum written in a sentence.

It might be easier to have backwards entry enabled for this exercise.

Module 33. These Instructions from 'Young Einstein Mathematics educational software by Maths Practice are Copyright. Copyright Maths Practice P/L 2003 ©