EXERCISE 1.3

1).** Estimate:**

a) 730 + 998

**Ans.** Rounding off to hundreds

730 = 700

998 = 1000

Hence 730 + 998 = 700 + 100

= 1700

b) 796 – 314

**Ans.** Rounding off to hundreds

796 = 800

314 = 300

Hence 796 – 314 = 800 – 300

= 500

c) 12,904 + 2,888

**Ans.** Rounding off to thousands

12,904 = 13,000

2,888 = 3,000

Hence 12,904 + 2,888 = 13,000 + 3000

= 16000

d) 28,292 – 21,496

**Ans.** Rounding off to thousands

28,292 = 28,000

21,496 = 21,000

Hence 28,292 – 21,496 = 28,000 – 21,000

= 7,000

2).** Make ten more such examples of addition, subtraction and estimation of their outcome.
**a) 422 + 319

**422 = 400**

Ans.

Ans.

**319 = 300**

400-300 = 100

**b)5,432 – 1,692**

**5,432 = 5,000**

Ans.

Ans.

**1,692 = 2,000**

**5,000 – 2,000 = 3000**

**c) 7,214 – 3,807**

**7,214 = 7,000**

Ans.

Ans.

**3,807 = 4,000**

**7,000 – 4,000 = 3,000**

**d)569 – 319**

**569 = 600**

Ans.

Ans.

**319 = 300**

**600– 300 = 300**

**e)639 + 587**

**639 = 600**

Ans.

Ans.

**587 = 600**

**600**

**+**600 = 1200

**f) 1697 – 876**

**1,697 = 2,000**

Ans.

Ans.

**876 = 900**

**2,000 – 900 = 1,100**

**f)6,772 + 5329**

**6,772 = 7,000**

Ans.

Ans.

**5,329 = 5,000**

**7,000 + 5,000 = 12,000**

**g) 3,692 + 2269**

**3,692 = 4,000**

Ans.

Ans.

**2,269 = 2,000**

**4,000 + 2,000 = 6,000**

**h) 8,762 – 4,921**

**8,762 = 9,000**

Ans.

Ans.

**4,921 = 5,000**

**9,000 – 5,000 = 4,000**

**i)2,659 + 4,217**

**2,659 = 3,000**

Ans.

Ans.

**4,217 = 4,000**

**3,000 + 4,000 = 7,000**

**3).**

**Give a rough estimate (by rounding off to nearest hundred) and also a closer estimate (by rounding off to nearest tens):**

a) 439 + 334 + 4,317

**Ans.**Rounding off to nearest hundreds

439 + 334 + 4,317 = 400 + 300 + 4,300

= 5,000

Rounding off to nearest tens

439 + 334 + 4,317 = 440 + 330 + 4,320

= 5,090

b) 1,08,734 – 47,599

**Ans.**Rounding off to nearest hundred

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

**Ans.**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

**Ans.**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 = 4,89,300 – 48,400

= 4,40,900

**Make four more of such examples**

1) 5,621 – 1,219

**Ans.** Rounding off to nearest hundred

5,621 – 1,219 = 5,600 – 1,220

=4,400

Rounding off to nearest tens

5,621 – 1,219 = 5,620 – 1,220

= 4,400

2) 337 + 769 + 438

**Ans.** Rounding off to nearest hundred

337 + 769 + 438 = 300 + 800 + 400

= 1,500

Rounding off to nearest tens

337 + 769 + 438 = 340 + 770 + 440

= 1,550

3) 12,762 + 3,593

**Ans.** Rounding off to nearest hundred

12,762 + 3,593 = 12,800 + 3,600

= 16,400

Rounding off to nearest tens

12,762 + 3,593 = 12,760 + 3,590

= 16,350

4) 9,737 – 3,871

**Ans.** Rounding off to nearest hundred

9,737 – 3,871 = 9,700 – 3,900

= 5,800

Rounding off to nearest tens

9,737 – 3,871 = 9,740 – 3,870

= 5,870