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Find the average of the first 20 multiples of 9.
Answer & Solution
Correct Answer:
Option
B
First 20 multiple of 9
$$\eqalign{ & {\text{Average}} = \frac{{90 + 99}}{2} \cr & = 45 + 49.5 \cr & = 94.5{\text{ Answer}} \cr & \cr & {\bf{Alternate \,Solution:}} \cr & {\text{Average}} = \frac{{{\text{First term}} + {\text{Last term}}}}{2} \cr & = \frac{{9 + 180}}{2} \cr & = 4.5 + 90 \cr & = 94.5 \cr} $$
$$\eqalign{ & {\text{Average}} = \frac{{90 + 99}}{2} \cr & = 45 + 49.5 \cr & = 94.5{\text{ Answer}} \cr & \cr & {\bf{Alternate \,Solution:}} \cr & {\text{Average}} = \frac{{{\text{First term}} + {\text{Last term}}}}{2} \cr & = \frac{{9 + 180}}{2} \cr & = 4.5 + 90 \cr & = 94.5 \cr} $$
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