Question
Find how many six-digit numbers can be formed from the digits 2, 3, 4, 5, 6 and 7 (with repetitions), if:
the numbers formed must be divisible by 25
the numbers formed must be divisible by 25
Answers
R_scott
6^4
the 1st four digits can be any of the six , the last two must be 2 5
the 1st four digits can be any of the six , the last two must be 2 5
oobleck
must end in 25, 50, 75 or 00
6^4 * 4
6^4 * 4
oobleck
Oops. Go with R_Scott. I neglected to omit 0 as a choice.
oobleck
Oops again
25 and 75 are both allowed, so 6^4 * 2
25 and 75 are both allowed, so 6^4 * 2
R_scott
yup ... 75 is included ... thanks, oobleck