Maths Puzzles

 I will give you the solution of bonus question first.  The answer is infinite speed Question was :   Tom wants to travel from San Francisco to  Los Angeles and back - a round trip -  with an average speed of 50 mph. If you are feeling very patriotic change the name of the person to Suresh and cities to Delhi and Agra.  Due to traffic, he could travel only at 25 mph on the way to Los Angeles. What must be his speed on return journey in order to get an average speed of 50 mph. Here is  why Let us distance between the two cities is x.  So Tom wants to travel the round trip in - 2x/50 hours - the distance being 2x = x/25 hours . The total time = x/25 Now for onward journey he has taken x/25 hours - x miles with the speed of 25 mph. So which means he has to cover the rest of the distance - x miles in a time of total time - x/25 = x/25 - x/25 = 0 hours The speed needed will be x/0 = infinite.  And the other question was  How do we get ...

 Today I have a simple puzzle and a bonus puzzle.     Can you get 10 using the numbers 1 1 5 and 8. You have to use all numbers. You can use any operator. Bonus puzzle :   Tom wants to travel from San Francisco to  Los Angeles and back - a round trip -  with an average speed of 50 mph. If you are feeling very patriotic change the name of the person to Suresh and cities to Delhi and Agra.  Due to traffic, he could travel only at 25 mph on the way to Los Angeles. What must be his speed on return journey in order to get an average speed of 50 mph. Believe me, the solution is really interesting.  By the way, if you like numbers, you may love my app Shataka . Give it a try.    You will find the solution to both the puzzles here . 

This puzzle is about a birthday. The day before yesterday I was 25. The next year I will be 28. This is true only one day in a year. What day is my Birthday ?

 This puzzle is not quite simple.  Find a number such that it is divisible by 9, and when we remove the right most digit, it will be divisible by 8. When you remove the next right most digit, it will be divisible by 7. And so on.  ABCDEFGHI should be divisible by 9 ABCDEFGH must be divisible by 8 ABCDEFG must be divisible by 7 and so on until AB must be divisible by 2 A must be divisible by 1. The solution to the puzzle is here

 Solution to puzzle 11: The monk will light both ends of one incense stick and one end of second incense stick. By 30 minutes, first stick will completely burn out and second stick will burn out half. Now the monk will light the other end of second stick. Now the second stick will burn in half the time of 30 minutes. That is, it will burn out in another 15 minutes.  By the times both sticks burn out, it will be 45 minutes. Puzzle 12 : Cards, cards This puzzle is from readers digest. A small number of cards has been lost from a complete pack. If I deal among four people, three cards remain. If I deal among three people, two remain and if I deal among five people, two cards remain. How many cards are there? Guessing game  Before I close this post, I will show you a guessing game. Guess any number. Now double the number. Add 10 to it. Next halve the number. Subtract original number from it. Now your answer is 5. Is it not?  So, how do people do that? Simple.  L...

 Solution to puzzle 2: There is no missing dollar.  The lawyers paid 30 dollars to the hotel of which they got back 5 dollars. Which means they paid 25 dollars to the hotel. And they paid 2 dollars to the waiter as tip. So the total amount they spent is 25+2 = 27 dollars. They each had paid 10 dollars initially and they got back one dollar each. Which means they each spent 9 dollars. 9 X 3 = 27 dollars.  Balanced!! Puzzle 3 : A sweet treat  You and Patrick have a candy competition. There is a pile of 100 caramel candies and one mint candy. Each of you have to take minimum 1 and not more than 5 candies at a time. The person who gets to pick up last candies will have mint candy as a prize which you love very much.   Patrick has let you decide who goes first.  Now who should be the first one to pick candies in order for you to win the race?   Hint : Try with 10 candies at first.