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How to solve Puzzle part-4

This page is for fun. I am writing this page so that freshers as well as seniors can think logically.I don't think freshers need to panic during 1st round of interview --the written test where the puzzle use to puzzle them.Everybody if we try to solve 5 puzzles per day and 60 days of preparation is taken, that is more than enough to crack an interview.

Lets talk about Puzzle

  • There is a number that is 2 times the sum of its digits. What is this number?
for a two digit number say xy it is actually written 10x+y
so 10x+y=2(x+y)
only possible when x=1 and y=8
so the required number 18
  •  If a clock takes 7seconds to strike 7, how long will the same clock take to strike 10?
The clock strikes for the first time at the start and takes 7 seconds for 6 intervals-thus for one interval time  taken=7/6.
Therefore, for 10 seconds there are 9 intervals and time taken is 9*7/6=10 and 1/2 seconds.
  • A ship went on a voyage. After it had traveled 180 miles a plane started with 10 times the speed of the ship.    Find the distance when they meet from starting point.
Say speed of ship=x miles/hour
Say they meet at 180+y miles.
so ship will take y/x hours to go there
by that time plane will cover the required distance 180+y and planes speed is 10 times of ship=10x miles
so (180+y)/10x=y/x
equating we will get y=20
so the the distance is 180+y=200 miles
  • There is a 3 digit number. 3rd number is the square root of the 1st digit. 2nd digit is the sum of 1st and 3rd.And that number is divisible by 2,3,6,7. What is that number?

say the number is xyz
where x=z*z-----1
and it is divisible by 2,3,6,7 i.e  any multiplier of 2*3*6*7=42 that will satisfy the conditions
the three digit multiplier of 42

so the required number is 462

  • A rich merchant had collected many gold coins. He did not want anybody to know about them. One day, his wife asked, "How many gold coins do we have?"
    After pausing a moment, he replied, "Well! If I divide the coins into two unequal numbers, then 37 times the difference between the two numbers equals the difference between the squares of the two numbers."
    The wife looked puzzled. Can you help the merchant's wife by finding out how many gold coins do they have?

Let, total no. of gold coins= x 
Let, y and z be two numbers such that x = y + z (y not equal to z) 
Given, 37(y - z) = (y^2) - (z^2) 
Therefore, 37(y - z) = (y + z)(y - z) 
Hence, total no. of gold coins= x = y + z = 37
Puzzle source-software_jobs yahoo groups
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