Asked by Rebecca
How many 3 digit numbers can be formed from the digits 2,3,5,6,7 and 9 which are divisible by 5 and none of the digits is repeated?
Answers
Answered by
Steve
come on, do some thinking.
If a number is divisible by 5, it must end in 5 or 0. In this case, 5 must be the 3rd digit.
That leaves 2,3,6,7,9 for the other two digits.
So, there are 5 ways to pick the 1st digit. Once it has been picked, there are only 4 choices for the 2nd digit.
So, there are 5*4 = 20 ways to form the 3-digit number.
If a number is divisible by 5, it must end in 5 or 0. In this case, 5 must be the 3rd digit.
That leaves 2,3,6,7,9 for the other two digits.
So, there are 5 ways to pick the 1st digit. Once it has been picked, there are only 4 choices for the 2nd digit.
So, there are 5*4 = 20 ways to form the 3-digit number.