ssr300
What is the probability of getting a number on the first throw greater than that on the second throw when a dice is thrown twice?
A. 1/6
B. 2/3
C. 5/12
D. 7/12
E. 5/6
Easy to understand method:
Numbers in brackets are numbers rolled in 2nd throw.
First throw equals 1:
Favorable case when 1st throw > 2nd throw is (not possible) = 0.
Unfavorable case when 1st throw <= 2nd throw is (1,2,3,4,5,6). = 6
First throw equal 2:
Favorable case when 1st throw > 2nd throw is (1) = 1
Unfavorable case when 1st throw <= 2nd throw is (2,3,4,5,6) = 5
First throw equal 3:
Favorable case when 1st throw > 2nd throw is (1,2) = 2
Unfavorable case when 1st throw <= 2nd throw is (3,4,5,6) = 4
First throw equal 4:
Favorable case when 1st throw > 2nd throw is (1,2,3) = 3
Unfavorable case when 1st throw <= 2nd throw is (4,5,6) = 3
First throw equal 5:
Favorable case when 1st throw > 2nd throw is (1,2,3,4). = 4
Unfavorable case when 1st throw <= 2nd throw is (5,6) = 2
First throw equal 6:
Favorable case when 1st throw > 2nd throw is (1,2,3,4,5) = 5
Unfavorable case when 1st throw <= 2nd throw is (6) = 1
Probabality = Total Favorable/Total favorable + unfavorable
=15/36
=5/12