In a frequency distribution, the mid-value of a class is 15 and the class intervals is 4. The lower limit of the class is 10          (b)  12            (c)  13        (d)  14

Explanation

Let the lower limit be `l` and upper limit be `u`.
Then, `u−l=4`...(1)
and `(u+l)/2=15`
​ or `u+l=30`...(2)
Subtracting (2) and (1)
u+l−u+l=`30−4`
`2l=26`
`l=13`
Thus, lower limit =`13`