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Question
A box contains 5 marbles each having a weight of 156 grams. The box also contains 25 marbles each having a weight of 114 grams. What is the average weight of all the marbles in the box?
A
121 grams.
B
122 grams.
C
120 grams.
D
119 grams.
Soln.
Ans: a
Ans: a
The weighted average = ${5 × 156 + 25 × 114}/30$, which equals ${780 + 2850}/30$ = 121.