Skill: Estimate differences

To estimate a difference, round the numbers first, then subtract the rounded numbers.

Example: Estimate $4{,}782-2{,}146$.

1. Choose a place to round.
   Round to the nearest hundred because both numbers have hundreds places.

2. Round each number.

   • $4{,}782$ rounds to $4{,}800$ because the tens digit is $8$.
   • $2{,}146$ rounds to $2{,}100$ because the tens digit is $4$.

3. Subtract the rounded numbers.

$$4{,}800-2{,}100=2{,}700$$

So, the estimated difference is:

$$\boxed{2{,}700}$$

The estimate tells us that the exact difference should be close to $2{,}700$. It is useful for checking whether an exact subtraction answer makes sense.