The digits 2, 3, 5 and 7 are arranged randomly to form a four-digit number. What is the probability that the number is odd? Express your answer as a common fraction.
Notice that the 2 could be in the first, second or third position. And for each of these, the other numbers can be arranged in 3! = 6 ways.
So 3 x 6 = 18
And all four numbers can be arranged in 24 ways.
So
18 / 24 =
3 / 4 probability that the number is odd
$${\frac{{\mathtt{3}}}{{\mathtt{4}}}}$$
+83 
