Cogito
Grade 5 Math · Chapter 1 · Lesson 5
Rounding Decimals
Which mark is it closer to?
10 problems · about 15 minutes · 5.NBT.A.4
What this lesson teaches
The child rounds decimals to any place using a number line.
- Rounding asks which mark is nearer.
- Find the two neighbours, then the midpoint.
- Exactly halfway rounds up by agreement.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Comparing Decimals to Thousandths: Which is bigger, 0.608 or 0.61?
Answer 0.61.
Why 0.610 beats 0.608.
Review — Thousandths: In 0.914, what digit is in the thousandths place?
Answer 4
Why The 4.
Warm Up
Straightforward practice. Get the method working first.
4 problemsRound 7.63 to the nearest whole number.
Answer 8
Why 8.
What question does rounding really ask?
Answer Which mark is it nearer to?
Why Rounding is a question about nearness.
Round 4.62 to the nearest whole number.
Answer 5
Why Past 4.5.
Round 4.28 to the nearest whole number.
Answer 4
Why Under 4.5.
Build It Up
The same ideas with more to keep track of.
2 problemsRound 9.5 to the nearest whole number.
Answer 10
Why Exactly halfway rounds up.
Round 12.49 to the nearest whole number.
Answer 12
Why Just under halfway.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Measurement: Round 2.83 to the nearest tenth. What is the tenths digit?
Answer 8
Why 2.8, so the tenths digit is 8.
The Price: Round 6.5 to the nearest whole number.
Answer 7
Why 7.