Q. The average income of 40 persons is 4200 Rs. and that of an other 35 persons is 4000 Rs. The average income of the whole group is :
Answer: $latex 4106 \frac{2}{3}Rs.&s=1$
Notes: Average income of whole group = $latex = \frac{4200\times 40+4000\times 35}{75}&s=1$ $latex = \frac{168000+140000}{75}&s=1$ $latex = \frac{308000}{75} = 4106\frac{2}{3}Rs.&s=1$ Hence option [B] is the right answer.

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