CBSE Class –VI Mathematics
NCERT Solutions
Chapter 1 Knowing Our Numbers (Ex. 1.3)

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
By rounding off to nearest hundreds, 730 rounds off to 700 and 998 rounds off to 1000
Estimated sum = 700 + 1000 = 1700
(b) 796 - 314
By rounding off to nearest hundreds, 796 rounds off to 800 and 314 rounds off to 300
Estimated difference = 800 - 300 = 500
(c) 12,904 + 2,888
By rounding off to nearest thousands, 12904 rounds off to 13000 and 2888 rounds off to 3000
Estimated sum = 13000 + 3000 = 16000
(d) 28,292 - 21,496
By rounding off to nearest thousands, 28292 rounds off to 28000 and 21496 rounds 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) 1,08,734 – 47,599
(c) 8325 – 491
(d) 4,89,348 – 48,365
Answer: (a) 439 + 334 + 4317
Rounding off to nearest hundreds 439, 334 and 4317 may be rounded off to 400, 300 and 4300 respectively.
Estimated sum = 400 + 300 + 4300 = 5000
Rounding off to nearest tens, 439, 334 and 4317 may be rounded off to 440, 330 and 4320 respectively.
Estimated sum = 440 + 330 + 4320 = 5090
(b) 1,08,734 – 47,599
Rounding off to nearest hundreds 1,08,734 and 47,559 may be rounded off to 1,08,700 and 47,600 respectively.
Estimated difference = 1,08,700 - 47,600 = 61100
Rounding off to nearest tens 1,08,734 and 47,559 may be rounded off to 1,08,730 and 47,600 respectively.
Estimated difference = 1,08,730 - 47,600 = 61130
(c) 8325 – 491
Rounding off to nearest hundreds 8325 and 491 may be rounded off to 8300 and 500 respectively.
Estimated difference = 8300 - 500 = 7800
Rounding off to nearest tens 8325 and 491 may be rounded off to 8330 and 490 respectively.
Estimated difference = 8330 - 490 = 7840
(d) 4,89,348 – 48,365
Rounding off to nearest hundreds 4,89,348 and 48,365 may be rounded off to 4,89,300 and 48,400 respectively.
Estimated difference = 489300 - 448400 = 440900
Rounding off to nearest tens 4,89,348 and 48,365 may be rounded off to 4,89,350 and 48,370 respectively.
Estimated difference = 489350 - 48370 = 440980
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