25.3 Histograms — Practise

1. H A class of width $8$ has frequency $24$. Find the frequency density.
2. H The class $10<x\leq30$ has frequency $40$. Find its width and frequency density.
3. H A histogram bar has width $6$ and frequency density $4$. Find the frequency.
4. H Class A has width $5$ and frequency $15$. Class B has width $10$ and frequency $20$. Find both densities and state which bar is taller.
5. H A class from $20$ to $35$ has frequency density $1.6$. Find its frequency.
6. H A class $0\leq x<4$ has frequency $12$. Find its frequency density.
7. H A histogram bar has width $12$ and density $2.5$. Find the frequency.
8. H A class has frequency $18$ and density $3$. Find its class width.
9. H Classes $0<x\leq5$, $5<x\leq15$, $15<x\leq20$ have frequencies $10, 20, 15$. Find the density for each class.