If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55 and 60, then the average marks of all the students is
Options:
A . 55
B . None of these
C . 53.33
D . 54.68
Answer: Option D Answer: (d)Using Rule 10, If the average of '$n_1$' numbers is $a_1$ and the average of '$n_2$' numbers is $a_2$, then average of total numbers $n_1$ and $n_2$ is$Average = {n_1a_1 + n_2a_2}/{n_1 + n_2}$The required average marks= ${55×50+60×55+45×60}/{55+60+45}$= ${2750+3300+2700}/{160}$= $8750/160$ = 54.68
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