The sum of two numbers is equal to $25$ and their difference is $20$. The ratio of the two numbers is

The students in three classes are in the ratio $2:3:5$. If $20$ students are increased in each class,the ratio changes to $4:5:7$. The total number of students before the increase was:

In a school,there were $1554$ students and the ratio of the number of boys to girls was $4:3$. After a few days,$30$ girls joined the school but some boys left; as a result,the ratio of boys to girls became $7:6$. The number of boys who left the school is:

There is a ratio of $5:4$ between two numbers. If $40\%$ of the first number is $12$,then $50\%$ of the second number is:

Two numbers are in the ratio $1: 2$. If $7$ is added to both,their ratio changes to $3: 5$. The greatest number is

The number that must be added to each of the numbers $8, 21, 13$ and $31$ to make the ratio of the first two numbers equal to the ratio of the last two numbers is: