Problem Solving - 44

Samar tried to type his new 7-digit phone number on a form, but what appeared on the form was 39269, since the '4' key on his computer no longer works. His secretary has decided to make a list of all of the numbers that could be Samar's new number. How many numbers will there be on the list?

(A) 21
(B) 24
(C) 25
(D) 30
(E) 36

Answer: A

It is clear from the question that there are two 4's missing as it is a seven digit number.
Total number of ways of choosing places for these two missing 4's in these 7 digits is 7C2 = 21 Once you fix the place for these two 4's rest all numbers will occupy remaining places.