Compatible numbers are numbers you can divide easily. You can use compatible numbers to estimate quotients.

Estimate: 181 5.

Think: 20  5 = 4 200 5 = 40 So,   181 5 is about 40.

Estimating with Compatible Numbers

Estimate: 46 6 Think: What number times 6 has a product close to 46? 8 x 6 = 48 So,   46  6 is about 8.

Find where the quotient begins.

Estimate: 312 5 Try dividing hundreds. 5 < 3 Not enough hundreds Try dividing tens. 5 > 31 Enough tens So the quotient begins in the tens place. Find the first digit of the quotient. Think: About how many 5s in 31? 5 x 5 = 25 too small 5 x 6 = 30  31 is between 25 and 35. Try 6. 5 x 7 = 35 too big Since you are estimating, write zeros for the other digits. is about 60.