NCERT Solution For Class 6, Maths, Chapter 1, Knowing Our Numbers, Exercise 1.3 given below.
NCERT Solution For Class 6, Maths, Chapter 1, Knowing Our Numbers, Exercise 1.3
Q.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
Make ten more such examples of addition, subtraction and estimation of their outcome.
Ans: (a) 730 + 998
730 rounds off to 700
998 rounds off to 1000
Hence, Estimated sum = 700 + 1,000 = 1,700
(b) 796 – 314
796 rounds off to 800
314 rounds off to 300
Hence, Estimated difference = 800 – 300 = 500
(c) 12,904 + 2,888
12904 rounds off to 13000
2888 rounds off to 3000
Hence, Estimated sum = 13,000 + 3,000 = 16,000
(d) 28292 – 21496
28292 round off to 28000
21496 round off to 21000
Hence, Estimated difference = 28,000 – 21,000 = 7,000
Ten more such examples:
(i) 530 + 480 = 500 + 500 = 1000
(ii) 4937 + 6990 = 5000 + 7000 = 12000
(iii) 5392 – 3770 = 5000 – 4000 = 1000
(iv) 6440 – 3972 = 6000 – 4000 = 2000
(v) 3175 + 1204 = 3000 + 1000 = 4000
(vi) 7112 – 5292 = 7000 – 5000 = 2000
(vii) 910 + 575 = 900 + 600 = 1500
(viii) 6200 – 4800 = 6000 – 5000 = 1000
(ix) 6731 + 1800 = 7000 + 2000 = 9000
(x) 6485 – 3319 = 6000 – 3000 = 3000
Q.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 + 4,317
(b) 1,08,734 – 47,599
(c) 8325 – 491
(d) 4,89,348 – 48,365
Make four more such examples.
Ans: (a) 439 + 334 + 4,317
Round off to nearest hundreds
439 + 334 + 4,317 = 400 + 300 + 4,300 = 5000
Rounding off to nearest tens
439 + 334 + 4,317 = 440 + 330 + 4,320 = 5,090
(b) 1,08,734 – 47,599
Rounding off to nearest hundreds
1,08,734 – 47,599 = 1,08,700 – 47,600 = 61,100
Rounding off to nearest tens
1,08,734 – 47,599 = 1,08,730 – 47,600 = 61,130
(c) 8,325 – 491
Rounding off to nearest hundreds
8,325 – 491 = 8,300 – 500 = 7,800
Rounding off to nearest tens
8,325 – 491 = 8,330 – 490 = 7,840
(d) 4,89,348 – 48,365
Rounding off to nearest hundreds
4,89,348 – 48,365 = 4,89,300 – 48,400 = 4,40,900
Rounding off to nearest tens
4,89,348 – 48,365 = 4,89,350 – 48,370 = 440980
Q.3. Estimate the following products using general rule: (a) 578 × 161 (b) 5281 × 3491 (c) 1291 × 592 (d) 9250 × 29
Make four more such examples.
Ans: (a) 578 × 161
578 rounded off to 600
161 rounded off to 200
The estimated product = 600 × 200 = 1,20,000
(b) 5,281 × 3,491
5281 rounded off to 5,000
3491 rounded off to 3,500
The estimated product = 5,000 × 3,500 = 1,75,00,000
(c) 1,291 × 592
1291 rounded off to 1,300
592 rounded off to 600
The estimated product = 1,300 × 600 = 7,80,000
(d) 9,250 × 29
9250 rounded off to 9000
29 rounded off to 30
The estimated product = 9,000 × 30 = 2,70,000