1.

The mode of the following frequency distribution is 46 and the total frequency is 150. Find the missing frequencies x and y.

Answer» Here, we are given total frequency is `150`.
`6+8+17+x+42+30+y+8 = 150`
`=> x+y+111 = 150`
`=>x+y = 39`
It means, both `x` and `y` does not exceed `42`.
So, our modal class wil be `40-50`.
Now, Mode can be given by formula,
`Mode = l+(f_1-f_0)/(2f_1-f_0-f_2)**h`
Here, `l =` Lower limit of modal class `= 40`
`f_1 = ` Frequency of Modal class `= 42`
`f_2 = ` Frequency of Pre Modal class `= x`
`f_3 = ` Frequency of Succeeding Modal class `= 30`
`h =` Class interval `= 10`
Putting these values in Mode formula,
`Mode = 40+(42-x)/(84-30-x)**10 = 40+(42-x)/(54-x)**10`
We are given, `Mode = 46`
`=>40+(42-x)/(54-x)**10 = 46`
`=> (42-x)/(54-x)**10 = 6`
`=> (42-x)/(54-x) = 6/10`
`=> (42-x)/(54-x) = 3/5`
`=>210-5x = 162-3x`
`=>2x = 48`
`=> x = 24`
`=>y = 39-24 => y = 15`


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