Question

A code consists of four different digits from 1 to 9, inclusive. What is the probability of selecting a code that consists of four consecutive digits but not necessarily in order? Express your answer as a common fraction.

Answer 1

a*b will be largest when a = 9 and b = 8 [or vice-versa]

c*d will be smallest when c =2 and d =1 [ or vice-versa]

Explanation:

The largest possible difference is

9 * 8 - 2*1 =

72 - 2 =

70 or

The largest possible difference is

9.8 - 1.2 =

8.6