Estimation (Intro) — Answer Key
Part A: Sort the Words
Sort each word or number into the correct category box.
1. Sort each number by how it rounds to the nearest 10.
Rounds DOWN
244261 Rounds UP
153555 15, 35, and 55 end in 5 and always round up. 24, 42, and 61 have ones digits under 5, so they round down.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. Round 15 to the nearest 10: 20
15 is halfway between 10 and 20. The rule says numbers ending in 5 round up, so 15 becomes 20.
2. Round 25 to the nearest 10: 30
25 ends in 5, so it rounds up to 30, never down to 20. The 5 rule pushes us to the next ten.
3. Round 45 to the nearest 10: 50
45 has ones digit 5, so it rounds up to the next ten, which is 50.
4. Round 65 to the nearest 10: 70
65 ends in 5. The 5 rule sends it up to the next ten, 70.
5. Round 85 to the nearest 10: 90
85 ends in 5, so it rounds up to 90, the next ten above it.
Part C: True or False?
Read each statement. Circle True or False.
1. The number 25 rounds to 20.
True False
25 ends in 5, and the rule says round up. So 25 rounds to 30, not down to 20.
2. The number 35 rounds to 40.
True False
35 ends in 5, so it rounds up to the next ten, which is 40.
3. The number 75 rounds to 70.
True False
75 ends in 5, so it rounds UP to 80. It never rounds down when the ones digit is 5.
4. The number 55 rounds to 60.
True False
55 ends in 5, so it rounds up to 60. The 5 rule sends numbers to the next ten.