R is 80% more efficient than S. If S alone can make a book in 90 days, then R alone can make the book in how many days?

A man misses a train by 1 hour if he travels at a speed of 4 kmph. If he had increased his speed to 5 kmph, he would gave still missed the train by 24 minutes. At what speed should he have travelled so that he reached the station exactly on time?

Three triangles are marked out of a bigger triangle at the three vertices such that each side of each of the smaller triangles is one-third as long as each corresponding side of the bigger triangle. The ratio of the area of the three small triangles taken together to that of the rest of the bigger triangle is ?

A man buys 10 oranges for Rs. 3 and sells 8 for Rs. 3. Calculate his gain percent.

15% of a number, when added to 30% of another, gives 24% of the sum of the two numbers. The bigger number is 4 more than the smaller one. What are the numbers?

A ball, thrown vertically upward, rises to a height of 80 m and returns to its original position. The magnitude of its displacement after 7 s of motion will be ____. (take g = 10 m/s2)

The sum of the present ages of a father and his son is 60 yrs. Six years ago, fathers age was five times the age of the son. After 6 yrs, son's age will be

Which of the following is one of the saltiest lakes in the world?