Here we're going to look at how we can make numbers by adding or taking away.
If we add two numbers together we are going to make a bigger number.
If we start with a number and take away we are going to make a smaller number.
When we add large numbers we can break them down into tens and units to make our job easier.
So if we're adding $37$37 to a number, we can make it easier by adding $10$10, $10$10, $10$10 and $7$7!
This makes our job of adding easier, we can also work backwards, adding $3$3 tens and $7$7 units means our starting number and landing number are $37$37 units apart, $10+10+10+7=37$10+10+10+7=37.
Let's take a look at how we can make new numbers by adding or taking away.
Use the sliders below to try adding and subtracting!
Worked Examples
QUESTION 1
Which of the options below make $31$31? There might be more than one right answer.
$22+9$22+9
A$27+4$27+4
B$23+8$23+8
C$21+6$21+6
D
QUESTION 2
Which of the options below make $37$37? There might be more than one right answer.
$45-8$45−8
A$41-8$41−8
B$30+7$30+7
C$36+1$36+1
D
QUESTION 3
Use the numbers to answer the questions below.
$20+15$20+15
$18+12$18+12
$39-9$39−9
$22+8$22+8
Identify the target number that 3 of the 4 groups of numbers make.
What is the target number of the odd one out.
How can we change the sum of the odd one out to make it match the target number in part a).
$20+15-5$20+15−5
A$20+15+0$20+15+0
B$20+15+5$20+15+5
C