Ratio and Proportion

The number of mainas and parrots in an aviary is in the ratio of (4x + 5) : 4x. If 25 mainas and 10 parrots are added to the aviary, then, the ratio would change to 5: 3. How many mainas are there in the aviary at initial?

The cost of printing a book increased from Rs. 96 to Rs. 120 from the year 2013 to 2018, such that the total money spent on printing books by a printing press increased in the ratio 5 ∶ 6. If the printing press printed 200 books in the year 2013, how many books did they print in the year 2018?

There are 240 workers and an amount of Rs. 2880 is to be divided among them. The ratio of total amount received to men and women is 5 : 4 and the ratio of the amount given to each man and each woman is 5 : 8. Find the number of men.

4 years hence, the ratio of ages A and B will be 5: 7 and 6 years hence, the ratio of ages will be 11: 15, then and their present ages.

A and B started a business in partnership. The ratio between the investments of A and B was 5: 4. If A invested for 12 months and at the end of the year the ratio of prot was 15: 8, then for how much time B invested?