| Class Mark | $10$ | $15$ | $20$ | $25$ | $30$ | $35$ | $40$ |
| Frequency | $4$ | $20$ | $40$ | $45$ | $30$ | $25$ | $5$ |
(ii)
| Class Interval | $10–20$ | $20–40$ | $40–60$ | $60–80$ | $80–100$ |
| Frequency | $9$ | $17$ | $15$ | $20$ | $14$ |
Solution:-
Steps to draw a histogram for given frequency distributions,
1. Take $1cm=10$ units on the y– axis and plot frequency.
2.Take $1cm=10$ units on the y– axis and plot class interval.
3. Hence, record the given data in the graph.
4. Also mark two more midpoints of zero frequency on x – axis at the start and at the end.
5. Finally the points connect using straight lines.
(ii)
Solution:-
Steps to construct histograms for given frequency distributions,
1. Take $1cm=10$ units on the x– axis and plot frequency.
2. Take $1cm=10$ units on the y– axis and plot class interval.
| Class Interval | Class mark | Frequency |
| $10–20$ | $(10+20)/2=30/2=15$ | $9$ |
| $20–40$ | $(20+40)/2=60/2=30$ | $17$ |
| $40–60$ | $(40+60)/2=100/2=50$ | $15$ |
| $60– 80$ | $(60+80)/2=140/2=70$ | $20$ |
| $80–100$ | $(80+100)/2=180/2=90$ | $14$ |
3. So, in the graph mark the points $(15,9)$, $(30,17)$, $(50,15)$, $(70,20)$, $(90,14)$.
4. Also mark two more midpoints of zero frequency at the start and at the end on x – axis. 5. Finally Connect the points using straight lines