Estimation (Intro) — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Which number rounds to 50?
A) 43
B) 47
C) 56
D) 61
47 rounds to 50 because its ones digit 7 is 5 or more. 43 rounds to 40, 56 rounds to 60, and 61 rounds to 60.
2. Which number rounds to 30?
A) 24
B) 26
C) 35
D) 37
26 rounds to 30 because its ones digit 6 is 5 or more. 24 rounds to 20, 35 rounds to 40, and 37 rounds to 40.
3. Which number rounds to 80?
A) 73
B) 77
C) 85
D) 92
77 rounds to 80 because its ones digit 7 is 5 or more. 73 rounds to 70, 85 rounds to 90, and 92 rounds to 90.
4. Which number does NOT round to 40?
A) 36
B) 38
C) 42
D) 46
46 has ones digit 6, so it rounds up to 50, not 40. The others, 36, 38, and 42, all round to 40.
Part B: Fill in the Blank
Write the correct answer on each line.
1. Round 58 to the nearest 10: 60
58 has ones digit 8, which is 5 or more, so 58 rounds up to 60.
2. Round 31 to the nearest 10: 30
31 has ones digit 1, which is less than 5, so 31 rounds down to 30.
3. Estimate 44 + 37 by rounding first: 80
44 rounds to 40 and 37 rounds to 40. Then 40 + 40 = 80, so the estimate is 80.
4. Estimate 82 - 48 by rounding first: 30
82 rounds to 80 and 48 rounds to 50. Then 80 - 50 = 30, so the estimate is 30.
5. Estimate 29 + 62 by rounding first: 90
29 rounds to 30 and 62 rounds to 60. Then 30 + 60 = 90, so the estimate is 90.