A can do a piece of work in 5 days and B in 4 days. How long will they take to do the same work when working together

The sum of the present ages of father and son is 90 years. 10 years earlier the ratio of their ages was 5:2. The present age of the father is:

A person spends 25% of his annual income on house rent, 15% on education of children and 45% on other items. If he saves INR 14400 annually, then the person's total income is:

A man sells an article at a loss of 10%. If he had sold it for INR 75 more he would have gained 20%. The cost price of the article is (in Rs.):

A merchant buys 20 kgs of a variety of rice at INR 14 per kg and another 40 kgs of rice at INR 10 per kg. He mixes them and sells 1/3  of the mixture at INR 12.50 per kg. At what rate should he sell the remaining mixture so as to earn a profit of 25% on the whole outlay

A litre of water weights a kilogram, a litre of another liquid weights 1.340 kilograms. A mixture of the two weights 1.270 kilograms per litre. The ratio of their volumes in a litre of the mixture is: