alanforde800Maximus wrote:The average of 20, 60 and 180 is twice the average of 10, 30, and which of the following ?
1)10
2)30
3)60
4)90
5)180
For the average of 20, 60, and 180 to be twice the average of 10, 30, and x, the SUM of 20, 60, and 180 must be twice the SUM of 10, 30, and x.
Sum of 20, 60 and 180 = 20+60+180 = 260.
Since this sum must be twice the sum of 10, 30 and x, we get:
260 = 2(10+30+x)
130 = 10+30+x
x = 90.
The correct answer is
D.
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