Question

The mid value of a class interval is $42$. If the class size is $10$ then the upper and lower limits of the class are:

• A. $47$ and $37$
• B. $37$ and $47$
• C. $37.5$ and $47.5$
• D. $47.5$ and $37.5$

Answer 1

The correct option is A $47$ and $37$

Let the lower limit be $l$ and upper limit be $u$.
Then, $u-l=10...\left(1\right)$
and $\frac{u+l}{2}=42$ or $u+l=84...\left(2\right)$
Subtracting $\left(2\right)$ and $\left(1\right)$,
$u+l-u+l=84-10$
$2l=74$
$l=37$
Thus, lower limit $=37$ and upper limit $=37+10=47$