Of a set of 30 numbers, average of 1st 10 numbers is equal to average of last…
2026
Of a set of 30 numbers, average of 1st 10 numbers is equal to average of last 20 numbers. The sum of last 20 numbers is?
- A.
2 x sum of last 10 numbers
- B.
2 x sum of 1st 10 numbers
- C.
sum of 1st 10 numbers
- D.
Cannot be determined
Attempted by 1670 students.
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Correct answer: B
Let the common average of the first 10 numbers and the last 20 numbers be a.
Sum of the first 10 numbers = 10a.
Sum of the last 20 numbers = 20a (since their average is also a).
Therefore the sum of the last 20 numbers = 20a = 2 × 10a = 2 × (sum of the first 10 numbers).
So the correct answer is: the sum of the last 20 numbers is twice the sum of the first 10 numbers.