What is the sum of all 3 digit positive integers that can be formed using the digits 1, 5, and 8, if the digits are allowed to repeat within a number?
A. 126
B. 1386
C. 3108
D. 308
E. 13986
My working:
3 spots: d1, d2, d3
d1 = 3 ways
d2 = 3 ways
d3 = 3 ways
total 27 ways in which number can be made using the given three digits.
So, the sum will have (9*1)+(9*5)+(9*8) = an 8 in the unit's digit.
But how do I choose between 3108 and 308?
Is there another way to solve?[/b]
A. 126
B. 1386
C. 3108
D. 308
E. 13986
My working:
3 spots: d1, d2, d3
d1 = 3 ways
d2 = 3 ways
d3 = 3 ways
total 27 ways in which number can be made using the given three digits.
So, the sum will have (9*1)+(9*5)+(9*8) = an 8 in the unit's digit.
But how do I choose between 3108 and 308?
Is there another way to solve?[/b]
