Estimation (Intro) — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Sam has 28 marbles and Ben has 42. About how many marbles do they have in all?
A) 60
B) 70
C) 80
D) 90
28 rounds to 30 and 42 rounds to 40. Then 30 + 40 = 70, so they have about 70 marbles together.
2. Lily read 19 pages on Monday and 31 on Tuesday. About how many pages did she read?
A) 40
B) 50
C) 60
D) 70
19 rounds to 20 and 31 rounds to 30. Then 20 + 30 = 50, so Lily read about 50 pages.
3. A jar had 61 candies. The class ate 38. About how many candies are left?
A) 20
B) 30
C) 40
D) 50
61 rounds to 60 and 38 rounds to 40. Then 60 - 40 = 20, so about 20 candies are left.
4. The store sold 47 apples in the morning and 23 in the afternoon. About how many apples were sold in all?
A) 60
B) 70
C) 80
D) 90
47 rounds to 50 and 23 rounds to 20. Then 50 + 20 = 70, so about 70 apples were sold.
Part B: Fill in the Blank
Write the correct answer on each line.
1. Nora baked 39 muffins and Kai baked 22. Estimate the total: 60
39 rounds to 40 and 22 rounds to 20. Then 40 + 20 = 60, so they baked about 60 muffins.
2. A zoo had 78 birds. 29 flew away. Estimate how many are left: 50
78 rounds to 80 and 29 rounds to 30. Then 80 - 30 = 50, so about 50 birds remain.
3. Max has 53 stickers and gets 18 more. Estimate his total: 70
53 rounds to 50 and 18 rounds to 20. Then 50 + 20 = 70, so Max has about 70 stickers.
4. There were 86 seats. 41 are taken. Estimate empty seats: 50
86 rounds to 90 and 41 rounds to 40. Then 90 - 40 = 50, so about 50 seats are empty.
5. Zoe has 32 red beads and 57 blue beads. Estimate the total: 90
32 rounds to 30 and 57 rounds to 60. Then 30 + 60 = 90, so Zoe has about 90 beads.