Page 25 - Start Up Mathematics_6

Therefore, estimated product of 5,281 and 3,849 5,000
= 5,000 × 4,000 × 4,000

= 2,00,00,000 2,00,00,000
(c) 1,291 × 592
Rounding off each factor to its greatest place:
1,291 rounded off to the nearest thousands is 1,000.
592 rounded off to the nearest hundreds is 600.
Therefore, estimated product of 1,291 and 592 1,000
= 1,000 × 600 × 600
= 6,00,000 6,00,000

Example 25: Estimate and compare with the actual sum:
(a) 870 + 986 (b) 10,866 + 2,368 (c) 2,345 + 5,679

Solution: (a) 870 + 986
Let’s round off to the nearest hundreds.
870 is rounded off to 900.
986 is rounded off to 1,000. 900
Therefore, estimated sum = 900 + 1,000 + 1,000
= 1,900 1,900
However, actual sum = 870 + 986
= 1,856 870

On rounding off 1,856 to its nearest hundreds, it becomes 1,900. + 986
1,856
Therefore, estimation is reasonable.

(b) 10,866 + 2,368
Let’s round off to the nearest thousands.
10,866 is rounded off to 11,000.
2,368 is rounded off to 2,000. 11,000
Therefore, estimated sum = 11,000 + 2,000 + 2,000
= 13,000 13,000

However, actual sum = 10,866 + 2,368
= 13,234 10,866
On rounding off 13,234 to its nearest thousands, it + 2,368
becomes 13,000. 13,234
Therefore, estimation is reasonable.
(c) 2,345 + 5,679 2,000
Let’s round off to the nearest thousands. + 6,000
2,345 is rounded off to 2,000. 8,000
5,679 is rounded off to 6,000.
Therefore, estimated sum = 2,000 + 6,000
2,345
= 8,000 + 5,679
However, actual sum = 2,345 + 5,679 8,024
= 8,024

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