Statisticshard · Past Paper
If the mean of $a, b$ is 10, and $b, c$ is 20, then $c-a$ is:
A10
B20
C30
D40
✓ Correct Answer: B — 20
$a+b = 20$, $b+c = 40$. Subtracting the first from the second gives $c-a = 20$.
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