## 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