How many three-digit numbers greater than 200 can be formed from the digits 1, 2, 6, 7, and 9, if the digits can be repeated?

. You have four choices for the first digit (2,6,7 or 9) because if the first digit is one, the number will be less than 200. You have five choices each for the second and third digit. 4*5*5=100 possible numbers.

2. This is simply 10C3=(10*9*8)/(3*2*1)=120.