Question

Out of 80 coins, one is counterfeit. What is the minimum number of weighing needed to find out the counterfeit coin?

Answer 1

First we divide the 80 coins into two halves -----> 40+40  (step 1)                      so we will be weighing its weight so one set will have less weight then again same ----------------> 20+20   again         (step 2)                    ----------------> 10+10 again           (step 3)                    ----------------> 5+5 again                (step 4)                      ----------------> 2+2+1                   (step 5) weighing the two sets of two coins if they found equal  the remained one is the required. else again------------------------->1+1      (step 6)then we will be getting.       so minimum 5, max 6