Primary 4 Mathematics · Chapter 9 · Answers and explanations
Lesson 9.5: Rounding Decimals (answers)
Section A · Multiple choice 4 marks
1. Round 4.7 to the nearest whole number.1 mark
(A) 4(B) 5(C) 4.5(D) 7
Answer: (B) 5The tenths digit is 7 (5 or more), so round up to 5.
2. Round 12.3 to the nearest whole number.1 mark
(A) 12(B) 13(C) 12.5(D) 10
Answer: (A) 12The tenths digit is 3 (less than 5), so round down to 12.
3. Round 6.48 to 1 decimal place.1 mark
(A) 6.4(B) 6.5(C) 6.6(D) 6.0
Answer: (B) 6.5The hundredths digit is 8, so round the tenths up: 6.5.
4. Which number does NOT round to 3.6 when rounded to 1 decimal place?1 mark
(A) 3.55(B) 3.58(C) 3.66(D) 3.64
Answer: (C) 3.663.66 has 6 hundredths, so it rounds up to 3.7. The others round to 3.6.
Section B · Write your answer 10 marks
5. Round 8.5 to the nearest whole number.1 mark
Answer: 9The tenths digit is 5, so round up.
6. Round 0.934 to 1 decimal place.1 mark
Answer: 0.9The hundredths digit is 3, so keep 0.9.
7. Round 7.995 to 2 decimal places.1 mark
Answer: 8.00The thousandths digit is 5, so round up: 7.99 becomes 8.00.
8. Round 15.62 to the nearest whole number.1 mark
Answer: 16The tenths digit is 6, so round up.
9. Round 2.149 to 2 decimal places.1 mark
Answer: 2.15The thousandths digit is 9, so round the hundredths up.
10. A ribbon is 3.46 m long. Round its length to 1 decimal place.
1 mark
Answer: 3.5 mThe hundredths digit is 6, so round up to 3.5 m.
11. Name the smallest and the greatest 2-decimal-place number that rounds to 5.3 when rounded to 1 decimal place.2 marks
Answer: 5.25 and 5.34Numbers from 5.25 up to 5.34 round to 5.3.
12. Sam rounds 6.45 to 1 decimal place and gets 6.4. Is he right? Explain.2 marks
Answer: No. It is 6.5The hundredths digit is 5, so round up to 6.5.
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