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 + 4,317 \\\\(b) 1,08,734 - 47,599 \\\\ (c) 8325- 491 \\\\ (d) 4,89,348 – 48,365

Answers (1)

(a) 439 + 334 + 4,317

Rounding off to nearest hundreds,

439 rounds off to 400

334 rounds off to 300

4317 rounds off to 4300,

Required sum = 400+300+4300

= 5000

Again, by rounding off to nearest tens,

439 rounds off to 440

334 rounds off to 330

4317 rounds off to 4320,

Required sum = 440+330+4320

= 5090

 

(b) 1,08,734 - 47,599

Rounding off to nearest hundreds,

1, 08,734 rounds off to 1, 08,700

47,599 rounds off to 47,600

Required difference = 1, 08,700 - 47,600

= 61100

Also, rounding off to nearest tens,

1, 08,734  rounds off to 1, 08,730

47,599  rounds off to 47,600

Required difference = 1, 08,730 - 47,600

= 61130

 

(c) 8325 - 491

Rounding off to nearest hundreds,

8325 rounds off to 8300

491 rounds off to 500

Required difference = 8300 - 500

= 7800

Also, rounding off to nearest tens,

8325 rounds off to 8330

491 rounds off to 490

Required difference = 8330 - 490

= 7840

 

(d) 4,89,348 - 48,365

Rounding off to nearest hundreds,

4,89,348 rounds off to 4,89,300

48,365 rounds off to 48,400

Required difference = 489300 - 48400

= 440900

Also, rounding off to nearest tens,

4,89,348 rounds off to 4,89,350

48,365 rounds off to 48,370

Required difference = 489350 - 48370

= 440980

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