The mid-value of a class interval is 42. If the class size is 10, then find the upper and lower limits of the class.

Mid value = 42 and class size = 10

The upper limit will be:  $42+\frac{10}{2}=42+5=47$

And the lower limit will be  $42-\frac{10}{2}=42-5=37$

Therefore, the lower-class limit and the upper-class limit will be 37 and 47 respectively.