एक दुकानदार के पास एक डिब्बा है जिसमें 150 काले पेन, 157 हरे पेन और 162 नीले पेन हैं। यदि एक पेन यादृच्छिक (random) रूप से निकाला जाता है, तो निकाले गए पेन के काले या हरे होने की क्या प्रायिकता है?

A box contains 'x + 4' red, 'x – 1' green and 'x – 5' blue balls. If two balls are drawn from the bag one after another without replacement, then the probability of getting one red and one green ball is equal to the probability of getting a sum equal to or more than 8 when two fair dice are rolled. Find the probability of drawing a red ball when one ball is drawn at random from the bag.

Four persons are chosen at random from a group containing 3 men, 2 women, and 4 children. The probability that exactly two of them are children is: