Question

6) How many different 5-digits zip codes can we have?

A) 100,000 B) 90,000 C) 81,000 D) 80,000

7) How many different 5-digits zip codes can we have with no zero as the first digit?

A) 100,000 B) 90,000 C) 81,000 D) 80,000

8) How many different 5-digits zip codes can we have with no zero as the first and last digit?

A) 100,000 B) 90,000 C) 81,000 D) 80,000

9) A security code consists of 4 parts, two digits first (zero is allowed) and 2 letters after (not case sensitive) How many different security codes are possible? A) 77,600 B) 67,600 C) 76,700 D) 76,600

10) A security code consists of 4 parts, two digit first (but the first digit can not be zero) and 2 letters after (not case sensitive but letter “o” is not allowed for both letters) How many different security codes are possible?

A) 56,250 B) 50,265 C) 56,625 D) 50,625

11) In how many ways Joe can dress up, if he has 6 shirts, 7 pants, and 5 pair of shoes?

A) 18 B) 180 C) 210 D) 201 11

Answer 1

6) Each digit can occur in 10 ways. So the number of different 5-digits zip codes is

7) The first digit can occur in 9 ways. Other digits can occur in 10 ways. So the number of different 5-digits zip codes is

7) The first and last digit can occur in 9 ways. Other digits can occur in 10 ways. So the number of different 5-digits zip codes is

8) Each of first two digits can occur in 10 ways. Each letter can occur in 26 ways. So the number of different security codes is ​​​​​​​.

9)The first and last digit can occur in 9 ways. Each letter can occur in 26-1=25 ways. So the number of different security codes is ​​​​​​​.

11) The number of ways of selecting one shirt from 6 is

The number of ways of selecting one pants from 7 is

The number of ways of selecting one pair of shoes from 5 is

The total number of ways Joe can dress up ​​​​​​​