Primary 4 Mathematics · Chapter 10 · Answers and explanations
Lesson 10.2: Subtraction of Decimals (answers)
Section A · Multiple choice 4 marks
1. 8.6 − 3.4 = ?1 mark
(A) 5.02(B) 12(C) 4.2(D) 5.2
Answer: (D) 5.2Tenths: 6 − 4 = 2. Ones: 8 − 3 = 5. So 5.2.
2. 7.45 − 2.31 = ?1 mark
(A) 5.14(B) 5.24(C) 4.14(D) 5.16
Answer: (A) 5.14Hundredths: 5 − 1 = 4. Tenths: 4 − 3 = 1. Ones: 7 − 2 = 5. So 5.14.
3. 6.3 − 2.7 = ?1 mark
(A) 4.6(B) 3.6(C) 4.4(D) 3.4
Answer: (B) 3.63 tenths − 7 tenths cannot be done. Rename 1 one as 10 tenths: 13 − 7 = 6. Ones: 5 − 2 = 3. So 3.6.
4. 9.02 − 3.57 = ?1 mark
(A) 6.55(B) 5.55(C) 5.45(D) 6.45
Answer: (C) 5.45Rename across the zero: 9.02 = 8 ones 9 tenths 12 hundredths. 12 − 7 = 5, 9 − 5 = 4, 8 − 3 = 5. So 5.45.
Section B · Write your answer 11 marks
5. 9.8 − 4.5 = ______1 mark
Answer: 5.3Tenths: 8 − 5 = 3. Ones: 9 − 4 = 5. So 5.3.
6. 8.75 − 3.42 = ______1 mark
Answer: 5.33Hundredths: 5 − 2 = 3. Tenths: 7 − 4 = 3. Ones: 8 − 3 = 5. So 5.33.
7. 7.2 − 3.9 = ______1 mark
Answer: 3.32 tenths − 9 tenths cannot be done. Rename: 12 − 9 = 3. Ones: 6 − 3 = 3. So 3.3.
8. 6.14 − 2.78 = ______1 mark
Answer: 3.36Rename: 14 − 8 = 6 hundredths. Tenths 0 after renaming, rename again: 10 − 7 = 3. Ones: 5 − 2 = 3. So 3.36.
9. 10 − 3.6 = ______2 marks
Answer: 6.4Write 10 as 10.0. 10.0 − 3.6 = 6.4.
10. 8 − 2.45 = ______1 mark
Answer: 5.55Write 8 as 8.00. 8.00 − 2.45 = 5.55.
11. 52.3 − 17.86 = ______2 marks
Answer: 34.44Write 52.3 as 52.30. 52.30 − 17.86 = 34.44.
12. A tank holds 25 ℓ of water. 8.75 ℓ are used. How much water is left?2 marks
Answer: 16.25 ℓ25.00 − 8.75 = 16.25. There are 16.25 ℓ left.
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