Solutions - Exercise 1 (E) | Number System | Class 6 Mathematics | Selina Concise Mathematics - Middle School.
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📂 Chapter 1 - Exercise 1 (E).
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-- EXERCISE - 1 (E) --
Q1. Estimate the sum of each pair of numbers to the nearest ten :
(i) 34 and 87
Solution :
34 round off to nearest ten = 30
87 round off to nearest ten = 90
Sum of two numbers = 30 + 90 = 120
Ans. Estimated Sum is 120
(ii) 78 and 18
Solution :
78 round off to nearest ten = 80
18 round off to nearest ten = 20
Sum of two numbers = 80 + 20 = 100
Ans. Estimated Sum is 100
(iii) 96 and 55
Solution :
96 round off to nearest ten = 100
55 round off to nearest ten = 60
Sum of two numbers = 100 + 60 = 160
Ans. Estimated Sum is 160
(iv) 76 and 62
Solution :
76 round off to nearest ten = 80
62 round off to nearest ten = 60
Sum of two numbers = 80 + 60 = 140
Ans. Estimated Sum is 140
(v) 457 and 175
Solution :
457 round off to nearest ten = 460
175 round off to nearest ten = 180
Sum of two numbers = 460 + 180 = 640
Ans. Estimated Sum is 640
(vi) 527 and 267
Solution :
527 round off to nearest ten = 530
267 round off to nearest ten = 270
Sum of two numbers = 530 + 270 = 800
Ans. Estimated Sum is 800
Q2. Estimate the sum of each pair of numbers to the nearest hundred :
(i) 336 and 782
Solution :
336 round off to nearest hundred = 300
782 round off to nearest hundred = 800
Sum of two numbers = 300 + 800 = 1100
Ans. Estimated Sum is 1100.
(ii) 270 and 495
Solution :
270 round off to nearest hundred = 300
495 round off to nearest hundred = 500
Sum of two numbers = 300 + 500 = 800
Ans. Estimated Sum is 800.
(iii) 4280 and 5295
Solution :
4280 round off to nearest hundred = 4300
5295 round off to nearest hundred = 5300
Sum of two numbers = 4300 + 5300 = 9600
Ans. Estimated Sum is 9600.
(iv) 30047 and 39287
Solution :
30047 round off to nearest hundred = 30,000
39287 round off to nearest hundred = 39,300
Sum of two numbers = 30,000 + 39,300 = 69,300
Ans. Estimated Sum is 69,300.
Q3. Estimate the sum of the following pairs of numbers to the nearest thousand :
(i) 53826 and 36455
Solution :
53826 round off to nearest thousand = 54,000
36455 round off to nearest thousand = 36,000
Sum of two numbers = 54,000 + 36,000 = 90,000
Ans. Estimated Sum is 90,000.
(ii) 56802 and 22475
Solution :
56802 round off to nearest thousand = 57,000
22475 round off to nearest thousand = 22,000
Sum of two numbers = 57,000 + 22,000 = 79,000
Ans. Estimated Sum is 79,000.
Q4. Estimate the following differences correct to the nearest ten :
(i) 82 - 27
Solution :
82 round off to nearest ten = 80
27 round off to nearest ten = 30
Difference of two numbers = 80 - 30 = 50
Ans. Estimated Difference is 50.
(ii) 96 - 36
Solution :
96 round off to nearest ten = 100
36 round off to nearest ten = 40
Difference of two numbers = 100 - 40 = 60
Ans.Estimated Difference is 60.
(iii) 508 - 248
Solution :
508 round off to nearest ten = 510
248 round off to nearest ten = 250
Difference of two numbers = 510 - 250 = 260
Ans. Estimated Difference is 260.
Q5. Estimate each difference to the nearest hundred :
(i) 769 - 314
Solution :
769 round off to nearest hundred = 800
314 round off to nearest hundred = 300
Difference of two numbers = 800 - 300 = 500
Ans. Estimated Difference is 500.
(ii) 856 - 687
Solution :
856 round off to nearest hundred = 900
687 round off to nearest hundred = 700
Difference of two numbers = 900 - 700 = 200
Ans. Estimated Difference is 200.
(iii) 6352 - 2086
Solution :
6352 round off to nearest hundred = 6400
2086 round off to nearest hundred = 2100
Difference of two numbers = 6400 - 2100 = 4300
Ans. Estimated Difference is 4300.
Q6. Estimate each difference to the nearest thousand :
(i) 45974 - 38766
Solution :
45974 round off to nearest thousand = 46,000
38766 round off to nearest thousand = 39,000
Difference of two numbers = 46,000 - 39,000 = 7,000
Ans. Estimated Difference is 7,000.
(ii) 76003 - 48399
Solution :
76003 round off to nearest thousand = 76,000
48399 round off to nearest thousand = 48,000
Difference of two numbers = 76,000 - 48,000 = 28,000
Ans. Estimated Difference is 28,000.
Q7. Estimate each of the following products by rounding off each number to the nearest ten :
(i) 49 × 52
Solution :
49 round off to nearest ten = 50
52 round off to nearest ten = 50
Product of two numbers = 50 x 50 = 2500
Ans. Estimated Product is 2500.
(ii) 63 x 38
Solution :
63 round off to nearest ten = 60
38 round off to nearest ten = 40
Product of two numbers = 60 x 40 = 2400
Ans. Estimated Product is 2400.
(iii) 27 x 54
Solution :
27 round off to nearest ten = 30
54 round off to nearest ten = 50
Product of two numbers = 20 x 50 = 1500
Ans. Estimated Product is 1500.
(iv) 53 x 85
Solution :
53 round off to nearest ten = 50
85 round off to nearest ten = 90
Product of two numbers = 50 x 90 = 4500
Ans. Estimated Product is 4500.
(v) 74 ×67
Solution :
74 round off to nearest ten = 70
67 round off to nearest ten = 70
Product of two numbers = 70 x 70 = 4900
Ans. Estimated Product is 4900.
(vi) 25 × 33
Solution :
25 round off to nearest ten = 30
33 round off to nearest ten = 30
Product of two numbers = 30 x 30 = 900
Ans. Estimated Product is 900.
Q8. Estimate each of the following products by rounding off each number to the nearest hundred :
(i) 477 ×213
Solution :
477 round off to nearest hundred = 500
213 round off to nearest hundred = 200
Product of two numbers = 500 x 200 = 1,00,000
Ans. Estimated Product is 1,00,000.
(ii) 624 × 236
Solution :
624 round off to nearest hundred = 600
236 round off to nearest hundred = 200
Product of two numbers = 600 x 200 = 1,20,000
Ans. Estimated Product is 1,20,000.
(iii) 333 x 247
Solution :
333 round off to nearest hundred = 300
247 round off to nearest hundred = 200
Product of two numbers = 300 x 200 = 60,000
Ans. Estimated Product is 60,000.
(iv) 537 x 283
Solution :
537 round off to nearest hundred = 500
283 round off to nearest hundred = 300
Product of two numbers = 500 x 300 = 1,50,000
Ans. Estimated Product is 1,50,000.
(v) 382 × 127
Solution :
382 round off to nearest hundred = 400
127 round off to nearest hundred = 100
Product of two numbers = 400 x 100 = 40,000
Ans. Estimated Product is 40,000.
(vi) 472 × 328
Solution :
472 round off to nearest hundred = 500
328 round off to nearest hundred = 300
Product of two numbers = 500 x 300 = 1,50,000
Ans. Estimated Product is 1,50,000.
Q9. Estimate each of the following products by rounding off the first number correct to the nearest ten and the other number correct to the nearest hundred :
(i) 28 x 287
Solution :
28 round off to nearest ten = 30
287 round off to nearest hundred = 300
Product of two numbers = 30 x 300 = 9,000
Ans. Estimated Product is 9,000.
(ii) 432 x 128
Solution :
432 round off to nearest ten = 430
128 round off to nearest hundred = 100
Product of two numbers = 430 x 100 = 43,000
Ans. Estimated Product is 43,000.
(iii) 48 x 165
Solution :
48 round off to nearest ten = 50
165 round off to nearest hundred = 200
Product of two numbers = 50 x 200 = 10,000
Ans. Estimated Product is 10,000.
(iv) 72 x 258
Solution :
72 round off to nearest ten = 70
258 round off to nearest hundred = 300
Product of two numbers = 70 x 300 = 21,000
Ans. Estimated Product is 21,000.
(v) 83 x 664
Solution :
83 round off to nearest ten = 80
664 round off to nearest hundred = 700
Product of two numbers = 80 x 700 = 56,000
Ans. Estimated Product is 56,000.
(vi) 44 × 250
Solution :
44 round off to nearest ten = 40
250 round off to nearest hundred = 300
Product of two numbers = 40 x 300 = 12,000
Ans. Estimated Product is 12,000.
Q10. Estimate each of the following quotients by rounding each number to the nearest ten :
(i) 87 ÷ 28
Solution :
87 round off to nearest ten = 90
28 round off to nearest ten = 30
Division of two numbers = 90 ÷ 30 = 3
Ans. Estimated quotient is 3.
(ii) 84 ÷ 23
Solution :
84 round off to nearest ten = 80
23 round off to nearest ten = 20
Division of two numbers = 80 ÷ 20 = 4
Ans. Estimated quotient is 4.
(iii) 77 ÷ 22
Solution :
77 round off to nearest ten = 80
22 round off to nearest ten = 20
Division of two numbers = 80 ÷ 20 = 4
Ans. Estimated quotient is 4.
(iv) 198 ÷ 24
Solution :
198 round off to nearest ten = 200
24 round off to nearest ten = 20
Division of two numbers = 200 ÷ 20 = 10
Ans. Estimated quotient is 10.
(v) 355 ÷ 26
Solution :
355 round off to nearest ten = 360
26 round off to nearest ten = 30
Division of two numbers = 360 ÷ 30 = 12
Ans. Estimated quotient is 12.
(vi) 444 ÷ 42
Solution :
444 round off to nearest ten = 440
42 round off to nearest ten = 40
Division of two numbers = 440 ÷ 40 = 11
Ans. Estimated quotient is 11.
(vii) 843 ÷ 33
Solution :
843 round off to nearest ten = 840
33 round off to nearest ten = 30
Division of two numbers = 840 ÷ 30 = 28
Ans. Estimated quotient is 28.
Q11. There are 768 houses in a town and about 7 people live in each house. Round off these two numbers to the nearest ten and estimate the total number of people living in the town.
Solution :
Number of houses in the town = 768
Round off to nearest ten = 770
Number of people in each house = 7
Round off to nearest ten = 10
Product of two numbers = 770 x 10 = 7700
Ans. Estimated number of people living in the town are 7700.
Q12. There are 514 mango trees in an orchard. The owner plans to plant 178 more mango trees. Estimate how many mango trees will be there in the orchard, correct to the nearest hundred ?
Solution :
Number of mango trees in an orchard = 514
Round off to nearest hundred = 500
Number of trees plan to be planted = 178
Round off to nearest hundred = 200
Total number of mango trees in the orchard = 500 + 200 = 700
Ans. Estimated number of mango trees in the orchard are 700.
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