Questions
1) Nanyang 2010 P6 Prelim paper 1 Qn 21
The cost of 3 mangoes is the same as the cost of 5 grapefruits.
The cost of 3 mangoes is also the same as the cost of 10 pears.
Find the ratio of the cost of a mango to the cost of a grapefruit to the cost of a pear.
(ans : 10 : 6 : 3)

Question: 
There were some boys and girls in a room.
If 24 boys leave the room, the total no. of students who remained in the room will be 7 times theno. of boys who remained the the room.
If 12 girls leave the room, the total no. of students who remained in the room will be 4 times the no. of boys.

How many students are there in the classroon?