Q.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) 108734 – 47599 (c) 8325 – 491 (d) 489348 – 48365

Make four more such examples.

(a) 439 + 334 + 4317 (b) 108734 – 47599 (c) 8325 – 491 (d) 489348 – 48365

Make four more such examples.

(a) 439 + 334 + 4317

Rounding off to nearest hundreds

439 + 334 + 4317

= 400 + 300 + 4300 = 5000

Rounding off to nearest tens

439 + 334 + 4317

= 440 + 330 + 4320 = 5090

(b) 108734 – 47599

Rounding off to nearest hundreds

108734 – 47599 = 108700 – 47600

= 61100

Rounding off to nearest tens

108734 – 47599 = 108730 – 47600

= 61130

(c) 8325 – 491

Rounding off to nearest hundreds

8325 – 491 = 8300 – 500

= 7800

Rounding off to nearest tens

8325 – 491 = 8330 – 490

= 7840

(d) 489348 – 48365

Rounding off to nearest hundreds

489348 – 48365 = 489300 – 48400

= 440900

Rounding off to nearest tens

489348 – 48365 = 489350 – 48370

= 440980

Four more examples are as follows

(i) 2343 + 1692

Rounding off to nearest hundreds

2343 + 1692

= 2300 + 1700

= 4000

Rounding off to nearest tens

2343 + 1692 = 2340 + 1690= 4030

(ii) 9086 – 1390

Rounding off to nearest hundreds

10000 – 1400 = 8600

= 8600

Rounding off to nearest tens

9086– 1390 = 9090 – 1390

= 7700

(iii) 1234 – 346

Rounding off to nearest hundreds

1234 – 346= 1200 – 300= 900

Rounding off to nearest tens

1234 – 346= 1230 – 350= 880

(iv) 2251+7654

Rounding off to nearest hundreds

2251+7654 = 2300+7700

= 10000

Rounding off to nearest tens

2251+7654 = 2250+7650

= 9900