maths - probability

A die is thrown twice. If the number obtained in the first throw is smaller than "3", the probability that the sum of the two number is greater than 6 is?

First throw Second Throw
Number 1 1
1 2
1 3
1 4
1 5
1 6
2 1
2 2
2 3
2 4
2 5
2 6
The total sum of throw is =2*6=12 throws
The number obtained in the first throw is smaller than "3" and the sum of the two number is greater than 6 is=3
Ther probability of event is =3/12
=1/4

Conditional Probability

Let A and B represent two events
The probability that B occurs after that A has already occurred is called a conditional probabilityd,denoted by P(B/A).


P(B/A)=P(A and B) over P(A)