Use doubles to find the sum of 7 + 8. Write the number sentence. +
The Correct Answer and Explanation is :
To find the sum of 7 + 8 using doubles, we can break the addition down into simpler steps. The idea of “doubles” refers to adding two identical numbers, like 1 + 1, 2 + 2, etc. By using the concept of doubles, we can create an addition sentence that helps us calculate the sum more easily.
Number Sentence:
7 + 8 can be rewritten as:
[ (7 + 7) + 1 ]
Explanation:
To apply doubles, first recognize that 7 + 7 is a double. The sum of 7 + 7 is 14. Now, we need to add the remaining 1 (because 8 is one more than 7).
Here’s the step-by-step breakdown:
- Start with the double:
[ 7 + 7 = 14 ] - Add the leftover number:
We still need to add 1 to get from 7 + 8. So we take the 14 we already have and add 1.
[ 14 + 1 = 15 ]
Thus, the sum of 7 + 8 is 15.
This method uses doubles to simplify the addition. By breaking down the problem, we first focus on adding two identical numbers (7 + 7), which is easy because it’s a “double.” Once we’ve handled the double, we only need to add a small leftover value (in this case, just 1) to reach the final sum.
Using doubles is helpful in mental math, as it allows us to use familiar, simple additions and then adjust with smaller numbers. This strategy can be extended to larger numbers or more complex problems, but the principle remains the same: break the addition into manageable steps based on known doubles.