math & puzzles Online Quiz - 106

Madagascar Island, there are x dodos in a particular year. 30 dodos in a thousand of the original population die every year and 25 dodos in a thousand of the original population are born every year. In how many years will the population of dodos halve itself ?

A cube is divided into 8 equal cubes. Each of these cubes is further sub-divided into 8 equal cubes. If the original cube’s sides are painted blue, then what is the probability that exactly 2 sides of a small cube is painted blue ?

There are 4 quarts in a gallon. A gallon of petrol sells for Rs.12 and a quart of the same petrol sells for Rs.5. The owner of a rental agency has 6 machines and each machine needs 5 quarts of petrol. What is the minimum amount of money he must spend to purchase enough petrol?

36 identical chairs must be arranged in rows with the same number of chairs in each row. Each row must contain at least 3 chairs and there must be at least 3 rows. A row is parallel to the front of the room. How many different arrangements are possible ?

The incomes of two people are in the ratio 4 : 5 and expenditures in the ratio 7 : 8 respectively. The total savings between the two of them is Rs.3000 and that is split in the ratio 1 : 2. Find their total income.

Mr.Ghosh wants to fence his square shaped field with each side measuring 120 ft. If the posts have to put at a distance of 12 ft each, how many posts are required ?