You can put this solution on YOUR website! First, note that the numbers 25 and 36 are perfect squares. In other words, and . So since 31 is in between 25 and 36, this means that the square root of 31 is in between 5 and 6. In other words, since , this means .
Notice how 31 is 6 units away from 25 and 5 units away from 36. So 31 is about the halfway point from 25 to 36. So a good approximation for is 5.5 since 5.5 is halfway between 5 and 6.
So
If we take the square root of 31 with a calculator, we get . So this shows us that our approximation is very close.