Ratio and Proportion

If the ratio of boys to girls in a class is 3:4 and there are 21 boys, how many girls are there?

A recipe requires 2 cups of sugar for every 5 cups of flour. If you have 15 cups of flour, how much sugar do you need?

The ratio of the ages of Amit and Rahul is 5:7. After 5 years, the ratio will be 6:8. What is Amit's current age?

A cricket team won 18 matches out of 30 matches played. What is the ratio of matches won to matches lost?

Two quantities are in the ratio 7:9. If their difference is 18, find the smaller quantity.

If 4 pens cost the same as 3 notebooks, and 5 notebooks cost Rs. 75, what is the cost of one pen?

(Revised) If 4 pens cost the same as 3 notebooks, and 5 notebooks cost Rs. 75, what is the cost of one pen?

The ratio of the length to the breadth of a rectangle is 5:3. If the perimeter is 64 cm, find the length of the rectangle.

In a Bollywood dance troupe, the ratio of male to female dancers is 7:8. If there are 45 female dancers, how many male dancers are there?