Question 1:
Estimate each of the following using general rule:
(a) 730 + 998
(b) 796 – 314
(c) 12,904 + 2,888
(d) 28,292 – 21,496
Answer 1:
(a) 730 round off to 700
998 round off to 1000
Estimated sum = 700 + 1000 = 1700
(b) 796 round off to 800
314 round off to 300
Estimated Difference = 800 - 300 = 500
(c) 12904 round off to 13000
2888 round off to 3000
Estimated sum = 13000 + 3000 = 16000
(d) 28292 round off to 28000
21496 round off to 21000
Estimated difference = 28000 - 21000 = 7000
Question 2:
Give a rough estimate (by rounding off to nearest hundreds) and also a closer estimate (by rounding off to nearest tens):
(a) 439 + 334 + 4317
(b) 1,08,737 – 47,599
(c) 8325 – 491
(d) 4,89,348 – 48,365
Answer 2:
(a) 439 round off to 400
334 round off to 300
4317 round off to 4300
Estimated sum = 400 + 300 + 4300 = 5000
(b) 108734 round off to 108700
47599 round off to 47600
Estimated difference = 108700 - 47600 = 61100
(c) 8325 round off to 8300
491 round off to 500
Estimated difference = 8300 - 500 = 7800
(d) 489348 round off to 489300
48365 round off to 48400
Estimated difference = 489300 - 48400 = 440900
Question 3:
Estimate the following products using general rule:
(a) 578 x 161
(b) 5281 x 3491
(c) 1291 x 592
(d) 9250 x 29
Answer 3:
(a) 578 x 161
578 round off to 600
161 round off to 200
The estimated product = 600 x 200 = 1,20,000
(b) 5281 x 3491
5281 round of to 5,000
3491 round off to 3,500
The estimated product = 5,000 x 3,500 = 1,75,00,000
(c) 1291 x 592
1291 round off to 1300
592 round off to 600
The estimated product = 1300 x 600 = 7,80,000
(d) 9250 x 29
9250 round off to 10,000
229 round off to 30
The estimated product = 10,000 x 30 = 3,00,000
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