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Re: How many five-digit even numbers can be formed using [#permalink]
There is something wrong. The answer is C. May someone check pls ?
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How many five-digit even numbers can be formed using [#permalink]
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huda wrote:
How many five-digit even numbers can be formed using \(2,6,3,0,\) and \(1\) only once?

(A) \(32\)
(B) \(36\)
(C) \(54\)
(D) \(60\)
(E) \(72\)


Since the resulting number must be EVEN, let's consider two possible cases:

case i: The unit's digit is 0
case ii: The unit's digit is 2 or 6

Question: Why am I considering those two cases separately?
Answer: I'm doing so because we DON'T get a 5-digit number if the first digit is 0 (e.g., 02631 is not a 5-digit number)

case i: The unit's digit (aka the 5th digit) is 0
So, there is 1 way to assign a value to the 5th digit.
There are now 4 digits remaining to choose from.
So, we can assign a value to the 1st digit in 4 ways.
We can assign a value to the 2nd digit in 3 ways.
We can assign a value to the 3rd digit in 2 ways.
We can assign a value to the 4th digit in 1 way.
By the Fundamental Counting Principal (FCP), we can complete all five steps (and create a 5 digit number) in (1)(4)(3)(2)(1) ways (= 24 ways)


case ii: The unit's digit is 2 or 6
Since the last digit is 2 or 6, there are 2 ways to assign a value to the last (5th) digit.
There are now 4 digits remaining to choose from, but one of those values is 0, which we can't choose for the 1st digit.
So, we can assign a value to the 1st digit in 3 ways.

At this point, we can assign any of the remaining three digits to the 2nd, 3rd and 4th places.
So, we can assign a value to the 2nd digit in 3 ways.
We can assign a value to the 3rd digit in 2 ways.
We can assign a value to the 4th digit in 1 way.
By the Fundamental Counting Principal (FCP), we can complete all five steps (and create a 5 digit number) in (2)(3)(3)(2)(1) ways (= 36 ways)

Total number of outcomes = 24 + 36 = 60

Answer: D

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Re: How many five-digit even numbers can be formed using [#permalink]
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Thank you Sir
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How many five-digit even numbers can be formed using [#permalink]
Using FCP
I. Last digit: 0
Then by FCP, 4x3x2x1=24
II. Last digit: 2
By FCP: 3x3x2x1= 18
III. Last digit: 2
By FCP: 3x3x2x1= 18
SUM OF ABOVE= 24+18+18= 60
Ans: D

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