7+8=(7+7)+1=15
Double
To get a double of a number, we add the same number to itself.
For example, double of 3 is 3 + 3 = 6.
Doubles plus 1 is a strategy used to add two consecutive numbers that is, when they are next to each other.
Now, using the fact for 7 + 7, we will solve the problem 7+8.
Here, we have 7+8 and as 8 is 1 more than 7.
So, we can write7+8 as:
7+ 8 = (7 + 7) + 1
= 14 + 1
= 15
Therefore by using the doubles we get the sum of 7 + 8 as 15.
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