If $P: Q = 8: 15$ and $Q: R = 3: 2$,then find $P: Q: R$.

The students in three classes are in the ratio $4:6:9$. If $12$ students are increased in each class,the ratio changes to $7:9:12$. Then the total number of students in the three classes before the increase is

If $a: b: c = 3: 4: 7,$ then the ratio $(a+b+c): c$ is equal to

The ratio between the present ages of $P$ and $Q$ is $5:7$ respectively. If the difference between $Q$'s present age and $P$'s age after $6$ years is $2$,what is the total of $P$'s and $Q$'s present ages (in years)?

In an army selection process,the ratio of selected to unselected candidates was $5:1$. If $100$ fewer candidates had applied and $20$ fewer had been selected,the ratio of selected to unselected candidates would have been $6:1$. How many candidates had applied for the process?

Which of the following represents a correct proportion?