Exercise: 2-B
Q1: Estimate the sum of each pair of numbers to the nearest ten:
i. 34 and 87
34 ≈ 30, 87 ≈ 90
30 + 90 = 120
ii. 78 and 18
78 ≈ 80, 18 ≈ 20
80 + 20 = 100
iii. 96 and 55
96 ≈ 100, 55 ≈ 60
100 + 60 = 160
iv. 76 and 62
76 ≈ 80, 62 ≈ 60
80 + 60 = 140
v. 457 and 175
457 ≈ 460, 175 ≈ 180
460 + 180 = 640
vi. 527 and 267
527 ≈ 530, 267 ≈ 270
530 + 270 = 800
Q2: Estimate the sum of each pair of numbers to the nearest hundred:
i. 336 and 782
336 ≈ 300, 782 ≈ 800
300 + 800 = 1100
ii. 270 and 495
270 ≈ 300, 495 ≈ 500
300 + 500 = 800
iii. 4280 and 5295
4280 ≈ 4300, 5295 ≈ 5300
4300 + 5300 = 9600
iv. 30047 and 39287
30047 ≈ 30000, 39287 ≈ 39300
30000 + 39300 = 69300
Q3: Estimate the sum of the following pairs of numbers to the nearest thousand:
i. 53826 and 36455
53826 ≈ 54000, 36455 ≈ 36000
54000 + 36000 = 90000
ii. 56802 and 22475
56802 ≈ 57000, 22475 ≈ 22000
57000 + 22000 = 79000
Q4: Estimate the following differences correct to the nearest ten:
i. 82 – 27
82 ≈ 80, 27 ≈ 30
80 – 30 = 50
ii. 96 – 36
96 ≈ 100, 36 ≈ 40
100 – 40 = 60
iii. 508 – 248
508 ≈ 510, 248 ≈ 250
510 – 250 = 260
Q5: Estimate each difference to the nearest hundred:
i. 769 – 314
769 ≈ 800, 314 ≈ 300
800 – 300 = 500
ii. 856 – 687
856 ≈ 900, 687 ≈ 700
900 – 700 = 200
iii. 6352 – 2086
6352 ≈ 6400, 2086 ≈ 2100
6400 – 2100 = 4300
Q6: Estimate each difference to the nearest thousand:
i. 45974 – 38766
45974 ≈ 46000, 38766 ≈ 39000
46000 – 39000 = 7000
ii. 76003 – 48399
76003 ≈ 76000, 48399 ≈ 48000
76000 – 48000 = 28000
Q7: Estimate each of the following products by rounding off each number to the nearest ten :
i. 49 × 52
49 ≈ 50, 52 ≈ 50
50 × 50 = 2500
ii. 63 × 38
63 ≈ 60, 38 ≈ 40
60 × 40 = 2400
iii. 27 × 54
27 ≈ 30, 54 ≈ 50
30 × 50 = 1500
iv. 53 × 85
53 ≈ 50, 85 ≈ 90
50 × 90 = 4500
v. 74 × 67
74 ≈ 70, 67 ≈ 70
70 × 70 = 4900
vi. 25 × 33
25 ≈ 30, 33 ≈ 30
30 × 30 = 900
Q8: Estimate each of the •following products by rounding off each number to the nearest hundred:
i. 477 × 213
477 ≈ 500, 213 ≈ 200
500 × 200 = 100000
ii. 624 × 236
624 ≈ 600, 236 ≈ 200
600 × 200 = 120000
iii. 333 × 247
333 ≈ 300, 247 ≈ 200
300 × 200 = 60000
iv. 537 × 283
537 ≈ 500, 283 ≈ 300
500 × 300 = 150000
v. 382 × 127
382 ≈ 400, 127 ≈ 100
400 × 100 = 40000
vi. 472 × 328
472 ≈ 500, 328 ≈ 300
500 × 300 = 150000
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 × 287
28 ≈ 30, 287 ≈ 300
30 × 300 = 9000
ii. 432 × 128
432 ≈ 430, 128 ≈ 100
430 × 100 = 43000
iii. 48 × 165
48 ≈ 50, 165 ≈ 200
50 × 200 = 10000
iv. 72 × 258
72 ≈ 70, 258 ≈ 300
70 × 300 = 21000
v. 83 × 664
83 ≈ 80, 664 ≈ 700
80 × 700 = 56000
vi. 44 × 250
44 ≈ 40, 250 ≈ 300
40 × 300 = 12000
Q10: Estimate each of the following quotients by rounding each number to the nearest ten:
i. 87 ÷ 28
87 ≈ 90, 28 ≈ 30
90 ÷ 30 = 3
ii. 84 ÷ 23
84 ≈ 80, 23 ≈ 20
80 ÷ 20 = 4
iii. 77 ÷ 22
77 ≈ 80, 22 ≈ 20
80 ÷ 20 = 4
iv. 198 ÷ 24
198 ≈ 200, 24 ≈ 20
200 ÷ 20 = 10
v. 355 ÷ 26
355 ≈ 360, 26 ≈ 30
360 ÷ 30 = 12
vi. 444 ÷ 42
444 ≈ 440, 42 ≈ 40
440 ÷ 40 = 11
vii. 843 ÷ 33
843 ≈ 840, 33 ≈ 30
840 ÷ 30 = 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.
768 ≈ 770, 7 ≈ 10
770 × 10 = 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 ?
514 ≈ 500, 178 ≈ 200
500 + 200 = 700
