Question 249759: How many 4-digit numbers can be formed from the Set A = (0,1,2,3,4,5,6) if there is no repetition.
My answer is n=6*6*5*4 = 720 4-DIGIT numbers can be formed.
How many of the numbers in part a are divisible by 5? (You must consider 2 cases.)
My answer is 720/5=144
what is the 2 cases I should be looking at?
Pls help
Answer by Edwin McCravy(20054)   (Show Source):
You can put this solution on YOUR website! How many 4-digit numbers can be formed from the Set A = (0,1,2,3,4,5,6) if there is no repetition.
My answer is n=6*6*5*4 = 720 4-DIGIT numbers can be formed.
That's right!
How many of the numbers in part a are divisible by 5? (You must consider 2 cases.)
My answer is 720/5=144
That's wrong!
what is the 2 cases I should be looking at?
Pls help
If a number is divisible by 5 it must end in either a 5 or a 0.
(0,1,2,3,4,5,6)
Choose the fourth digit first.
Case 1. Choose the fourth digit as 0
That leaves 6 ways to choose the first digit.
That leaves 5 ways to choose the second digit.
That leaves 4 ways to choose the third digit.
That's 6*5*4 = 120 ways
Case 2. Choose the fourth digit as 5
That leaves 5 ways to choose the first digit. (It can't be 0)
That leaves 5 ways to choose the second digit.
That leaves 4 ways to choose the third digit.
That's 5*5*4 = 100 ways
That's a total of 120 + 100 or 220 ways a 4 digit
number can end in 0 or 5.
Edwin
|
|
|
