If the fractions $$ {9\over11}$$, $$ {7\over9}$$, $$ {5\over6}$$ and $$ {11\over13}$$ are arranged in ascending order, which one will be the fourth?

The angle of elevation of the top of a tree 220 metres high from two points lies on the same plane are 30° and 45°. What is the distance (in metres) between the two points?

In the given figure, PQR is an equilateral triangle with side as 12 cm. S and T are the midpoints of the sides PQ and PR respectively. What is the area (in cm²) of the shaded region?

A pump can fill a cistern in 40 minutes and another pump can empty the filled up cistern in 1 hour. By mistake, without closing the second pump, the first pump is opened. The time in which the empty cistern will be filled up is

A work is done in 12 days by a team of 10 men, the same work is completed by a team of 10 women in 6 days. If both work together then in how many days the same work can be completed-

Vessels A and B contain mixture of milk and water in the ratios 4 : 5 and 5 : 1 respectively. In what ratio should quantities of mixture be taken from A and B to from a mixture in which milk to water is in the ratio 5 : 4 ? 

In two types of brass ratio of copper and zinc are 8: 3 and 15: 7 respectively. The ratio in which these two types of brass should be mixed, so that the ratio of copper and zinc in this new type of brass become 5: 2 is 

A number is divided into three parts such that three times of the first part, six times of the second part and eight times the third part are equals to each other. If the first part is Rs. 1600, what is the third part?