# Worksheet: Estimating Sums of Three-Digit Numbers: Compatible Numbers

In this worksheet, we will practice using compatible numbers like 25, 50, 75, and 100 to estimate the value of sums up to 1000.

Q1:

Compatible numbers are pairs of numbers that are easy to add, subtract, multiply, or divide mentally.

First, calculate the actual sum of the following: Second, use compatible numbers to estimate the sum of the following: Q2:

Use compatible numbers to estimate .

• A720
• B705
• C740
• D760

Q3:

Use compatible numbers to estimate .

• A500
• B440
• C403
• D300
• E400

Q4:

Pick the best estimate for this sum.

Hint: Use compatible numbers.

• A900
• B880
• C890
• D875

Q5:

Yesterday, Benjamin won 128 coins at the fair in the morning and 278 coins in the afternoon. Pick the best estimate for the total number of coins he won yesterday.

Hint: Use compatible numbers.

• A410
• B430
• C450
• D380

Q6:

Pick the best estimate for this sum.

Hint: Use compatible numbers.

• A810
• B850
• C900
• D890

Q7:

Pick the best estimate for .

Hint: Use compatible numbers.

• A580
• B600
• C590
• D550

Q8:

We can use compatible numbers to estimate sums.

Pick the calculation that best estimates this sum. • A
• B
• C
• D

Q9:

Pick the best estimate for this sum.

Hint: Use compatible numbers.

• A905
• B800
• C940
• D960

Q10:

Pick the best estimate for this sum.

Hint: Use compatible numbers.

• A395
• B385
• C375
• D400