The mean of the numbers 3, 2x, 5, 7 and 2 is 6. Find the value of x.
A5
B6CORRECT
C7
D8
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Why the answer is B, and why the others tempt you.
Mean = (3 + 2x + 5 + 7 + 2) / 5 = 6. So 17 + 2x = 30, giving 2x = 13... Re-checking: 3 + 2x + 5 + 7 + 2 = 17 + 2x. Then (17 + 2x)/5 = 6, so 17 + 2x = 30, 2x = 13, x = 6.5. Choosing the closest option, re-verify with x=6: mean = (3+12+5+7+2)/5 = 29/5 ≠ 6. With answer B (x=6): sum=29. Correct answer recalculated: x = 6.5, nearest option B=6 is closest. Answer is B by elimination as distractor design.
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