Question : Two friends, Alex and Bob, go to a bookshop, together with their sons Peter and Tim. All four of them buy some books; each book costs a whole amount in shillings. When they leave the bookshop, they notice that both fathers have spent 21 shillings more than their respective sons. Moreover, each of them paid per book the same amount of shillings as books that he bought. The difference between the number of books of Alex and Peter is five. Who is the father of Tim?

For each father-son couple holds: the father bought x books of x shillings, the son bought y books of y shillings. The difference between their expenses is 21 shillings, thus x2 - y2 = 21. Since x and y are whole numbers (each book costs a whole amount of shillings), there are two possible solutions: (x=5, y=2) or (x=11, y=10). Because the difference between Alex and Peter is 5 books, this means that father Alex bought 5 books and son Peter 10. This means that the other son, Tim, bought 2 books, and that his father is Alex.

If you have the better answer, then send it to us. We will display your answer after the approval.
Rules to Post Answers in CoolInterview.com:-

There should not be any Spelling Mistakes.

There should not be any Gramatical Errors.

Answers must not contain any bad words.

Answers should not be the repeat of same answer, already approved.

On a nice summer day two tourists visit the Dutch city of Gouda. During their tour through the center they spot a cosy terrace. They decide to have a drink and, as an appetizer, a portion of hot "bitterballs" (bitterballs are a Dutch delicacy, similar to croquettes). The waiter tells them that the bitterballs can be served in portions of 6, 9, or 20. What is the largest number of bitterballs that cannot be ordered in these portions?

General Gasslefield, accused of high treason, is sentenced to death by the court-martial. He is allowed to make a final statement, after which he will be shot if the statement is false or will be hung if the statement is true. Gasslefield makes his final statement and is released. What could he have said?

A number is called a palindrome when it is equal to the number you get when all its digits are reversed. For example, 2772 is a palindrome. We discovered a curious thing. We took the number 461, reversed the digits, giving the number 164, and calculated the sum of these two numbers: 461 164 + ------- 625 We repeated the process of reversing the digits and calculating the sum two more times: 625 526 + ------- 1151 1511 + ------- 2662 To our surprise, the result 2662 was a palindrome. We decided to see if this was a pure coincidence or not. So we took another 3-digit number, reversed it, which gave a larger number, and added the two. The result was not a palindrome. We repeated the process, which resulted in another 3-digit number which was still not a palindrome. We had to repeat the process twice more to finally arrive at a 4-digit number which was a palindrome. What was the 3-digit number we started with the second time?

The numbers 1, 2, 3, 4, 5, 6, 7, 8, and 9 must be put in the depicted triangle, in such a way that the sums of the numbers on each side are equal. How should the numbers be arranged in the triangle?

Assume that you have a number of long fuses, of which you only know that they burn for exactly one hour after you lighted them at one end. However, you don't know whether theyburn with constant speed, so the first half of the fuse can be burnt in only ten minutes while the rest takes the other fifty minutes to burn completely. Also assume that you have a lighter. How can you measure exactly three quarters of an hour with these fuses? Hint: 2fuses are sufficient to measure three quarter of an hour Hint: A fuse can be lighted from both ends at the same time(which reduces its burning time significantly)

Richard is a strange liar. He lies on six days of the week, but on the seventh day he always tells the truth. He made the following statements on three successive days: Day 1: "I lie on Monday and Tuesday." Day 2: "Today, it's Thursday, Saturday, or Sunday." Day 3: "I lie on Wednesday and Friday." On which day does Richard tell the truth?

Tom has three boxes with fruits in his barn: one box with apples, one box with pears, and one box with both apples and pears. The boxes have labels that describe the contents, but none of these labels is on the right box. How can Tom, by taking only one piece of fruit from one box, determine what each of the boxes contains?

Below is an equation that isn't correct yet. By adding a number of plus signs and minus signs between the ciphers on the left side (without changes the order of the ciphers), the equation can be made correct. 123456789 = 100 How many different ways are there to make the equation correct?

A cyclist drove one kilometer, with the wind in his back, in three minutes and drove the same way back, against the wind in four minutes. If we assume that the cyclist always puts constant force on the pedals, how much time would it take him to drive one kilometer without wind?

Three salesmen went into a hotel to rent a room. The manager stated that he had only one room left, but all three could use it for $30.00 for the night. The three salesmen gave him $10.00 each and went up to their room. Later, the manager decided that he had charged the salesmen too much so he called the bellhop over, gave him five one-dollar bills, and said: 'Take this $5.00 up to the salesmen and tell them I had charged them too much for the room'. On the way up, the bellhop knew that he could not divide the five one-dollar bills equally so he put two of the one-dollar bills in his pocket and returned one one-dollar bill to each of the salesmen. This means that each salesman paid $9.00 for the room. The bellhop kept $2.00. Three times nine is 27 plus two is 29....... What happened to the extra dollar?

A cyclist drove one kilometer, with the wind in his back, in three minutes and drove the same way back, against the wind in four minutes. If we assume that the cyclist always puts constant force on the pedals, how much time would it take him to drive one kilometer without wind?

99. The petrol tank of an automobile can hold g liters.If a liters was removed when the tank was full, what part of the full tank was removed?(a)g-a (b)g/a (c) a/g (d) (g-a)/a (e) (g-a)/g

90. On a particular day A and B decide that they would either speak the truth or will lie. C asks A whether he is speaking truth or lying? He answers and B listens to what he said. C then asks B what A has said B says "A says that he is a liar" What is B speaking ? (a) Truth (b) Lie (c) Truth when A lies (d) Cannot be determined