Skill: Estimate sums using rounding

To estimate a sum, round each addend to the specified place. Then add the rounded numbers.

Remember:

• Look at the digit immediately to the right of the place you are rounding to.
• If that digit is $5$ or greater, round up.
• If it is less than $5$, keep the rounding digit the same.
• Change the digits to the right into zeros.

Example: Estimate $3{,}746+2{,}189$ to the nearest hundred.

1. Round $3{,}746$ to the nearest hundred. The tens digit is $4$, so round down:

$$3{,}746\approx 3{,}700$$

2. Round $2{,}189$ to the nearest hundred. The tens digit is $8$, so round up:

$$2{,}189\approx 2{,}200$$

3. Add the rounded numbers:

$$3{,}700+2{,}200=5{,}900$$

So, the estimated sum is:

$$\boxed{5{,}900}$$