## Chapter 1: Knowing Your Numbers

## Exercise 1.3

**Q1. 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.**

(a) 730 round off to 700

998 round off to 1000

Estimated sum = 1700

(b) 796 round off to 800

314 round off to 300

Estimated difference = 500

(c) 12,904 round off to 13,000

2,888 round off to 3,000

Estimated sum = 16,000

(d) 28,292 round off to 28,000

21,496 round off to 21,000

Estimated difference= 7,000

**Q2. 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.**

(a) 439 round off to 400

334 round off to 300

4,317 round off to 4,300

Estimated sum = 5,000

(b) 1,08,734 round off to 1,08,700

47,599 round off to 47,600

Estimated difference = 61,100

(c) 8,325 round off to 8,300

491 round off to 500

Estimated difference = 7,800

(d) 4,89,348 round off to 4,89,300

48,365 round off to 48,400

Estimated difference = 4,40,900

**Q3. Estimate the following products using general rule: **

**(a) 578 x 161 **

**(b) 5281 x 3491 **

**(c) 1291 x 592 **

**(d) 9250 x 29 **

**Answer.**

**(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 **

5,281 round of to 5,000

3,491 round off to 3,500

The estimated product = 5,000 x 3,500 = 1,75,00,000

**(c) 1291 x 592 **

1,291 round off to 1,300

592 round off to 600

The estimated product = 1,300 x 600 = 7,80,000

**(d) 9250 x 29 **

9,250 round off to 10,000

229 round off to 30

The estimated product = 10,000 x 30 = 3,00,000