ML Aggarwal Class 6 Solutions for ICSE Maths Chapter 1 Knowing Our Numbers Ex 1.4
Question 1.
Round off each of the following numbers to their nearest tens:
(i) 77
(ii) 903
(iii) 70 1205
(iv) 999
Solution:
(i) 77
The digit at unit place is 7, which is greater than 5.
Hence, the rounded off number to nearest tens = 80.
(ii) 903
The digit at unit place is 3, which is less than 5.
Hence, the rounded off number to nearest tens = 900.
(iii) 1205
The digit at unit place is 5, which is equal to 5.
Hence, the rounded off number to nearest tens = 1210
(iv) 999
The digit at unit place is 9, which is greater than 5.
Hence, the rounded off number to nearest tens = 1000.
Question 2.
Estimate each of the following numbers to their nearest hundreds:
(i) 1246
(ii) 32057
(iii) 53961
(iv) 555555
Solution:
(i) 1246
The digit at tens place is 4, which is less than 5.
Hence, the rounded off number to nearest hundreds = 1200.
(ii) 32057
The digit at tens place is 5, which is equal to 5.
Hence, the rounded off number to nearest hundreds = 32100.
(iii) 53961
The digit at tens place is 6, which is greater than 5.
Hence, the rounded off number to nearest hundreds = 54000.
(iv) 555555
The digit at tens place is 5, which is equal to 5.
Hence, the rounded off number to nearest hundreds = 555600.
Question 3.
Estimate each of the following numbers to their nearest thousands:
(i) 5706
(ii) 378
(iii) 47,599
(iv) 1,09,736
Solution:
(i) 5706
The digit at hundred place is 7, which is greater than 5.
Hence, the rounded off number to nearest thounsands = 6000.
(ii) 378
The digit at hundred place is 3, which is less than 5.
Hence, the rounded off number to nearest thousands = 0.
(iii) 47,599
The digit at hundred place is 5, which is equal to 5.
Hence, the rounded off number to nearest thousands = 48000.
(iv) 1,09,736
The digit at hundred place is 7, which is greater than 5.
Hence, the rounded off number to nearest thousands = 1,10,000.
Question 4.
Give a rough estimate (by rounding off to nearest hundreds) and also a closer estimate (by rounding off to nearest tens):
(i) 439 + 334 + 4317
(ii) 8325 – 491
(iii) 1,08,734-47,599
(iv) 4,89,348 – 48,365
Solution:
(i) Rounding off to nearest hundreds 439 + 334 + 4317
= 400 + 300 + 4300 = 5000 Rounding off to nearest tens 439 + 334 + 4317
= 440 + 330 + 4320 = 5090
(ii) Rounding off to nearest hundreds 8325 – 491
= 8300 – 500 = 7800 Rounding off to nearest tens 8325 – 491
= 8330 – 490 = 7840
(iii) 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
(iv) 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 = 4,40,980
Question 5.
Estimate each of the following by rounding off each number nearest to its greatest place:
(i) 730 + 998
(ii) 5,290 + 17,986
(iii) 796-314
(iv) 28,292 – 21,496
Solution:
(i) 730 + 998
Rounding off 730 to its greatest place i.e. hundred place = 700
Rounding off 998 to its greatest place i.e. hundreds place = 1000
Hence, estimated sum = 700 + 1000 = 1700
(ii) 5,290 + 17,986
Rounding off 5,290 to its greatest place i.e. thousands place = 5000
Rounding off 17,986 to its greatest place i. e. thousands place = 18,000 Hence, estimated sum = 5,000 + 18,000 = 23,000
(iii) 796 – 314
Rounding off 796 to its greatest place i.e. hundreds place = 800 Rounding off 314 to its greatest place i.e. hundreds place = 300 Hence, estimated difference = 800 – 300 = 500
(iv) 28,292 – 21,496
Rounding off28,292 to its greatest place i.e. thousands place = 28,000 Rounding off 21,496 to its greatest place i. e. thousands place = 21,000 Hence, estimated difference = 28,000 – 21,000 = 7,000
Question 6.
Estimate the following products by rounding off each of its factors nearest to its greatest place:
(i) 578 × 161
(ii) 9650 × 27
Solution:
(i) 578 × 161
Rounding off 578 to its greatest place i.e. hundreds place = 600
Rounding off 161 to its greatest place i.e. hundreds place = 200
Hence, estimated product = 600 x 200 = 1,20,000
(ii) 9650 × 27
Rounding off 9650 to its greatest place i.e. thousands place = 10000
Rounding off 27 to its greatest place i.e. tens place = 30
Hence, estimated product = 10000 × 30 = 3,00,000
Question 7.
Estimate the following products by rounding off each of its factors nearest to its hundreds place:
(i) 5281 × 3491
(ii) 1387 × 888
Solution:
(i) 5281 x 3491
Rounding off 5281 to its hundreds place = 5300
Rounding off 3491 to its hundreds = 3500
Hence, estimated product = 5300 × 3500 = 1,85,50,000
(ii) 1387 × 888
Rounding off 1387 to its hundreds place = 1400
Rounding off 888 to its hundreds place = 900
Hence, estimated product = 1400 × 900 = 12,60,000