Of the 5 numbers whose average is 72, the first is 1/8 times the sum of other 4. The first number is .---------------
Let the first number be $$x$$ and sum of other four numbers be $$y$$
=> Average of five numbers = $$\frac{x + y}{5} = 72$$
=> $$x + y = 72 \times 5 = 360$$ ------------(i)
According to ques, => $$x = \frac{1}{8} \times y$$
=> $$y = 8x$$
Substituting value of $$y$$ in equation (i), we get :
=> $$x + 8x = 360$$
=> $$x = \frac{360}{9} = 40$$
=> Ans - (C)
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