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Mathematics

Estimate the following by rounding off each number to the nearest 1000:

(a) 8,756 + 5,234

(b) 12,845 - 6,379

Also write the actual answers and compare them with the estimates.

Number System

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Answer

(a) Rounding each number to the nearest 1000 :

8,756 → 9,000 (since 756 ≥ 500, round up)

5,234 → 5,000 (since 234 < 500, round down)

Estimated sum = 9,000 + 5,000 = 14,000.

Actual sum = 8,756 + 5,234 = 13,990.

Comparison : The estimate 14,000 is very close to the actual answer 13,990 (difference of only 10).

(b) Rounding each number to the nearest 1000 :

12,845 → 13,000 (since 845 ≥ 500, round up)

6,379 → 6,000 (since 379 < 500, round down)

Estimated difference = 13,000 - 6,000 = 7,000.

Actual difference = 12,845 - 6,379 = 6,466.

Comparison : The estimate 7,000 is close to the actual answer 6,466 (difference of 534).

Hence, (a) Estimated = 14,000 and Actual = 13,990; (b) Estimated = 7,000 and Actual = 6,466.

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