Remember
The opposite (inverse) of division is multiplication.
Example: 6 × 5 = 30 so we know that 30 ÷ 5 = 6.
When we estimate, we make a good guess based on what we know.
To estimate an answer, we round numbers off to make them easier to work with. For example, 598 ÷ 3 is not easy to calculate. If we round up 598 to 600, the calculation is much easier.
We know that 6 ÷ 3 = 2. So 600 ÷ 3 = 200.
We know that the answer to 598 ÷ 3 will be close to 20