# choosing at least twice a digit out of 10 digits

A six digits code chosen out of 0-9 digits. ‘003425’ for example. How many codes are there with at least two times the digit ‘7’?

• The number of codes without "7" is? The number of codes with exactly one "7" is? – peterwhy Nov 9 '14 at 13:34

• how many codes are there without digit $7$?
• how many codes are there with digit $7$ appearing exactly once?