Estimation (Intro) — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. Round 76 to the nearest 10: 80
76 has 7 tens and 6 ones. Since 6 is 5 or more, we add one ten and 76 rounds up to 80.
2. Round 93 to the nearest 10: 90
93 has 9 tens and 3 ones. Since 3 is less than 5, the tens stay the same and 93 rounds to 90.
3. Round 89 to the nearest 10: 90
89 has 8 tens and 9 ones. Since 9 is 5 or more, we add one ten and 89 rounds up to 90.
4. Estimate 34 + 58 by rounding first: 90
34 rounds to 30 and 58 rounds to 60. Then 30 + 60 = 90, so the estimate is 90.
5. Estimate 77 - 42 by rounding first: 40
77 rounds to 80 and 42 rounds to 40. Then 80 - 40 = 40, so the estimate is 40.
6. Round 99 to the nearest 10: 100
99 has 9 tens and 9 ones. Since 9 is 5 or more, we add one ten and 99 rounds up to 100.
7. Estimate 61 + 28 by rounding first: 90
61 rounds to 60 and 28 rounds to 30. Then 60 + 30 = 90, so the estimate is 90.
8. Round 82 to the nearest 10: 80
82 has 8 tens and 2 ones. Since 2 is less than 5, the tens stay and 82 rounds to 80.
9. Estimate 95 - 31 by rounding first: 70
95 rounds to 100 and 31 rounds to 30. Then 100 - 30 = 70, so the estimate is 70.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
62
→ 60
60
68
→ 70
70
81
→ 80
80
86
→ 90
90
62 rounds down to 60. 68 rounds up to 70. 81 rounds down to 80. 86 rounds up to 90. Each number pairs with a different ten.