Exercise 1F
Question 1
(a) 68 nearest ten is 70
53 nearest ten is 50
∴ Estimate sum = 70 + 50
= 120
(b) 466 hundred is 500
325 hundred ten is 300
∴ Estimate sum = 500 + 300
= 800
(c) 8379 nearest hundred is 8400
264 nearest hundred is 300
Estimate sum = 8400 + 300
= 8700
(d) 1693 nearest thousand is 2000
4509 nearest thousand is 5000
Estimate sum = 2000 + 5000
= 7000
(e) 27,619 nearest ten thousand is 30,000
53, 987 nearest ten thousand is 50,000
∴ Estimate sum = 30,000 + 50,000
= 80,000.
Question 2
(a) 898 nearest hundred is 900
345 nearest hundred is 300
Estimate difference = 900 – 300
= 600
(b) 839 nearest ten is 840
48 nearest ten is 50
∴ Estimate difference = 840 – 50
= 790
(c) 362 nearest hundred is 400
279 nearest hundred is 300
Estimate difference = 400 – 300
= 100
(d) 5718 nearest thousand is 6000
2014 nearest thousand is 2000
∴ Estimate difference = 6000 – 2000
= 4000.
(e) 73,284 nearest thousand is 70,000
39,541 nearest ten thousand is 40,000
∴ Estimate difference = 70000 – 40000
= 30000
Question 3
(a) 68 nearest ten is 70
7 is not rounded off
∴ Estimated product = 70 x 7
= 490
(b) 523 nearest ten is 500
16 nearest ten is 20
∴ Estimate product = 500 x 20
10000
(c) 517 nearest ten is 500
68 nearest ten is 70
∴ Estimate product = 500 x 70
= 35,000
(d) 74 nearest ten is 70
87 nearest ten is 90
∴ Estimate product = 70 x 90
= 6300
(e) 408 nearest hundred is 400
189 nearest hundred is 200
∴ Estimate product = 400 x 200
= 80,000
Question 4
(a) 123 ÷ 8 => 120 ÷ 8 = 15
∴ Estimate quotient = 15
(b) 157 ÷ 19 => 160 ÷ 20 = 8
∴ Estimate quotient = 8
(c) 958 ÷ 49 => 1000 ÷ 50 = 20
∴ Estimate quotient = 20
(d) 7982 ÷ 1728 => 8000 ÷ 2000 = 4
∴ Estimate quotient = 4
(e) 17,869 ÷ 8,759 => 18,000 ÷ 9000 = 2
∴ Estimate quotient = 2
Question 5
(a) 7680 nearest thousand is 8000
4293 nearest thousand is 4000
∴ Estimate sum = 8000 + 4000
= 12000
(b) 58,734 nearest ten thousand is 60,000
14,695 nearest ten thousand is 10,000
∴ Estimate difference = 60,000 – 10,000
= 40,000
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