What percent of 64 is 80?

Average of first 10 natural numbers is

Find the missing number in the sequence:

4, -8, 16, -32, 64, (____)

If 28 = 1 + 2 + 4 + x + y, where x and y are distinct factors of 28, find the value of xy.

 30% discount on Rs. 1000 and 2 successive discounts of 15% and 15% will have a difference of 

How many four-digit numbers, where the first two digits are equal and the last two digits are also equal, are perfect squares?

Lara and Eva are making bracelets. Lara takes 6 hours to prepare 32 bracelets, while Eva takes 5 hours to complete 40 bracelets. How much time will they take to make 100 bracelets working together?

A and B are playing a game with marbles where if a blue marble shows up they get 1 point, if a red marble shows up they lose 0.25 points, and if a yellow marble shows up they lose 0.125 points. If A plays for 65 chances and gets 37 points, then what is the possible number of yellow marbles when the number of red marbles shown is 17?

 A shepherd has 1 million sheep at the beginning of Year 2000. The numbers grow by x during the year. A famine hits his village in the next year and many of his sheep die. The sheep population decreases by y during 2001 and at the beginning of 2002, the shepherd finds that he is left with 1 million sheep. Which of the following is correct?

A and B can complete a work alone in an integral number of days. It is found that when they reduce their working hours by 4 hours per day, both took 5 days more than what they took earlier, although their usual working hours are different. If they do the work together with their usual working hours, then they can complete the work in little over