A box contains five sets of while there are 3 in each set. Each set of has one which is different from every other set, what is the least number of that must be removed from the box in order to claim with certainty that a pair of of the same colour has been removed?
(a) 6 (b) 7 (c) 8 (d) 9
Now, any further removal of from any set will ensure that removed ball is of the same colour as one of the already removed , thus constituting a pair of the removed ***** of the same colour.
Hence, minimum no. of removed ***** = 6
