Correct option is: C) 20
Since, class intervals 1-20, 21-40, 41-60 are of inclusive type,
So, we have to convert it into exclusive type of class intervals.
\(\because\) Difference between two consecutive intervals is 1.
\(\therefore\) We have to subtract \(\frac 12\) or 0.5 from lower limit of each class and add 0.5 in upper limit of each class to convert class intervals into exclusive type.
\(\therefore\) 0.5 - 20.5, 20.5-40.5, 40.5 - 60.5 are class intervals of exclusive type
Width of the class intervals = Upper limit - Lower limit
= 20.5 - 0.5 or 40.5 - 20.5 or 60.5 - 40.5 = 20
Hence, width of the class intervals is 20
Alternate Method:
\(\because\) Given class intervals 1-20, 21-40, 41-60 is of inclusive type.
\(\therefore\) Width of the class intervals = Upper limit - Lower limit + Difference between two consecutive classes
= 20-1 +1 or 40-21 + 1 or 60-41+1
= 20
