Adding and Subtracting Doubles

Remember the related subtraction facts for doubles facts.

1 + 1 = 2
2 – 1 = 1
6 + 6 = 12
12 – 6 = 6
2 + 2 = 4
4 – 2 = 2
7 + 7 = 14
14 – 7 = 7
3 + 3 = 6
6 – 3 = 3
8 + 8 = 16
16 – 8 = 8
4 + 4 = 8
8 – 4 = 4
9 + 9 = 18
18 – 9 = 9
5 + 5 = 10
10 – 5 = 5
10 + 10 = 20
20 – 10 = 10

Let's find difference of 18 and 9.

18 – 9 = ?

Consider the doubles fact:

9 + 9 = 18

Its related subtraction fact is:

18 – 9 = 9

So, the difference of 18 and 9 is 9.





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Help

The correct answer is

Remember :

The smallest number is the one that comes first while counting.

Solution :

To arrange the given numbers in order from smallest to greatest, find the smallest number among all the given numbers.

21,27,23

21 is the smallest number.