Find the average of the following sets of numbers.
693, 456, 876, 532, 934, 691, 596, 398, 682
- AOption (a)
550.50
- BOption (b)
750.80
- COption (c)
650.89
- DOption (d)
725.90
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Correct answer
650.89
Why this answer is correct
Shortcut Trick
Assume a base average of 600 and calculate deviations from it.
Deviations: +93, −144, +276, −68, +334, +91, −4, −202, +82
Sum of deviations = (93 + 276 + 334 + 91 + 82) − (144 + 68 + 4 + 202) = 876 − 418 = 458
Average deviation = 458 ÷ 9 ≈ 50.89
Actual Average = 600 + 50.89 = 650.89
∴ The correct answer is 650.89.
Alternate Method
Given observations: 693, 456, 876, 532, 934, 691, 596, 398, 682
Formula used: Average = Sum of observations ÷ Total number of observations
⇒ Sum = 693 + 456 + 876 + 532 + 934 + 691 + 596 + 398 + 682
⇒ Sum = 5858
⇒ Total count of numbers (n) = 9
⇒ Average = 5858 ÷ 9
⇒ Average = 650.8888...
∴ The correct answer is 650.89.
Additional Information
Sum of Deviations
The sum of the deviations of a set of observations from their arithmetic mean is always zero. ∑(xi − x̄) = 0.
Scaling Property
If every observation in a data set is increased/decreased by a constant 'k', the new average also increases/decreases by 'k'.
Combined Average Formula
If two groups have sizes n1, n2 and averages a1, a2, the combined average is (n1a1 + n2a2) ÷ (n1 + n2).







































