Mohan gets 3 marks for each correct sum and loses 2 marks for each wrong sum. He attempts 30 sums and obtains 40 marks. The number of sums solved correctly is:

If the price of petrol increases by 19% and Sunitha intends to spend only an additional 12 % on petrol, by what percent should she reduce the quantity of petrol purchased?

Average of ten positive numbers  is x. If each number is increased by 12%  then x is increased by

In an alloy, there is 12 % of copper, to get 69 kg of copper, how much alloy will be required? 

In a village, each of the 60 % of families has a cow; each of the 30 % of families has a buffalo and each of the 15 % of families has both a cow and a buffalo. in all there are 96 families in the village. How many families do not have a cow or a buffalo? 

The price of sugar is increased by 20 %. If the expenditure on sugar has to be kept the same as earlier, the ratio between the reduction in consumption and the original consumption is: 

Sumit got 186 marks in Science, 158 marks in Hindi and 78 marks in Maths. The maximum marks in Science is 220, 180 in Hindi and 130 in Maths. What is his approximate total percentage marks?