alleryIf the arithmetic mean of two positive numbers is 10, their sum must be:
ATwenty
BThirty
CFifty
DNinety
Answer & Solution
Correct answer: A. Twenty
1. The arithmetic mean of a and b is their sum divided by two.
2. Setting that equal to ten gives the sum directly.
3. From the arithmetic mean of 10 we get that a plus b is 20.
4. So the sum is twenty.
_Source: syllabus Mathematics, Ch 8 'Sequences and Series'_
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