Mathnasium #MathTricks: Number Sense (Subtraction)

By Mathnasium | October 18, 2021

Here is a number sense trick to help you calculate subtraction using mental math.

We want to find the difference of 100 – 76. Using our number sense, we turn to “friendly numbers” to calculate how far apart are 76 and 100.

Starting at 76, we can first find how far apart are 76 and 80 (the nearest multiple of 10) and get 4.

Then, we find how far apart are 80 and 100, and get 20.

So, 76 and 100 are 4 + 20 = 24 apart, and our final answer is

100 – 76 = 24.

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