**Estimation** is used to find an answer close to

the actual answer by solving an easier problem.

When an operation is involved, one way to estimate is to

round before adding, subtracting, multiplying, or dividing.

First, round both numbers to the nearest hundred.

Then, subtract.

6,400 - 600 = 5,800

The actual difference of 6,391 and 605 is 5,786.

So, 5,800 is a good estimate of the difference.

Another way to estimate is to use compatible numbers.

Compatible numbers are numbers that are

easier to add, subtract, multiply, or divide.

In a division problem, numbers are compatible if the dividend is easily divisible by the divisor.

To find compatible numbers, increase or decrease the dividend by a small amount so that it is divisible by the divisor.

Estimate 64 as 63, which is divisible by 7.