93
The mean of the following frequency distribution is $35$. Find the values of $x$ and $y$, if the sum of frequencies is $25$ :
Class
$0-10$
$10-20$
$20-30$
$30-40$
$40-50$
$50-60$
$60-70$
Frequency
$1$
$x$
$5$
$7$
$y$
$3$
$1$
Class
$0-10$
$10-20$
$20-30$
$30-40$
$40-50$
$50-60$
$60-70$
Frequency
$1$
$x$
$5$
$7$
$y$
$3$
$1$
Show SolutionHide Solution↓
Correct Table (2 Marks)
$\sum f_i = 25 \implies x + y = 8$ ..... (i) (1/2 Mark)
Mean $(\bar{x}) = \frac{605+15x+45y}{25} = 35$ (1/2 Mark)
$\implies 15x + 45y = 270$ or $x + 3y = 18$ ..... (ii) (1 Mark)
Solving (i) and (ii), we get $x = 3, y = 5$ (1/2 Mark + 1/2 Mark)
$\sum f_i = 25 \implies x + y = 8$ ..... (i) (1/2 Mark)
Mean $(\bar{x}) = \frac{605+15x+45y}{25} = 35$ (1/2 Mark)
$\implies 15x + 45y = 270$ or $x + 3y = 18$ ..... (ii) (1 Mark)
Solving (i) and (ii), we get $x = 3, y = 5$ (1/2 Mark + 1/2 Mark)