Question

There are 6561 balls are there out of them 1 is heavy. Find the minimum number of times the balls have to be weighted for finding out the heavy ball ?

A) 2414 B) 204 C) 87 D) 8

Answer 1

$\Large{\textsf{\pink{\underline{\underline{ANSWER}}}}}$

★ HERE IS THE SHORT METHOD TO DO THIS :

★ Take two balls randomly. If you are lucky, they will weigh different. The ball with the larger weight is the one you are looking for. The minimum number of times you need, is 1.

★ If you are looking for a sureshot method, divide the number of balls by the smallest prime divisor possible, here 3.

• For 6561 balls, you need to divide into groups of 3, then identify the heaviest group, and then further that heaviest group you will continue dividing until you come to 3 balls, then finally in 2 steps you will get the required ball.
• This means you need

= 3 ^ x = 6561 , where x will be your answer.

★ Here 8.