1fully worked

A class $10

1width $=15-10=5$Class width $=$ upper $-$ lower

2$\text{FD}=\dfrac{12}{5}=2.4$Frequency density $=$ frequency $\div$ width

Check - What is the class width here?

A $15$B $5$C $10$D $12$

2fully worked

A class $0

1width $=20-0=20$Class width $=$ upper $-$ lower

2$\text{FD}=\dfrac{30}{20}=1.5$Frequency density $=$ frequency $\div$ width

Check - Why can the frequency ($30$) be more than the frequency density ($1.5$)?

A a mistake – they should be equalB the density is spread over a width of $20$, so per unit it is smallC density is always biggerD frequency is always $1.5$

3you finish it

A class $20

1width $=32-20=12$Class width $=$ upper $-$ lower

2Frequency density $=$ frequency $\div$ width

Check - What is $18\div12$?

A $1.5$B $6$C $2.4$D $0.67$

4you do it all

A class $5

1Class width $=$ upper $-$ lower

2Frequency density $=$ frequency $\div$ width

Check - To go back from this bar to the frequency you would...

A multiply the density by the class widthB divide againC add the widthD square the density