There are 6 orange, 2 pink, 4 yellow and 3 green towels in a carton. What is the probability of picking up 2 orange towels randomly.

We know,
Probability = what we want/Total
Or = add; AND = multiply

We want 2 orange towels
That means to choose one AND then choose other from the remaining towels
There are 6 orange towels
Total 15 towels

So probability for two orange towels = 6/15 × 5/14
= 1/7 [Here we reduce the denominator i.e. the total number of towels because once we remove a towel from the box we do not put it back in the box.
So while removing the 2^nd towel, there are only 15 - 1 = 14 towels in the box.]