PERMUTATION:
How many even numbers less than 500 can be formed using the digits 1,2,3,4,5? Each digits may be used only once in any number.
(hinted: the answer is 28)

28

Step-by-step explanation:

It can be a one digit no.

_

2C1 = 2 (only two even options available)

It can be a 2 digit no.

_ _

The last digit has to be even for the no. to be even.

2C1 × 4C1 = 8 (2C1 for the last digit, 4C1 for the first)

It can be a 3 digit no.

_ _ _

First digit has to be less than 5 to be less than 500, and the last digit has to be even.

1) 2/4 _ 4

2C1 × 3C1 = 6 (2C1 to choose between 2 and 4, 3C1 for the second digit)

2) 1/3 _ 2/4

2C1 × 3C1 × 2C1 = 12 (2C1 to choose between 1 and 3, 3C1 for the second digit, 2C1 to choose between 2 and 4)

Total = 2 + 8 + (6 + 12)

= 28

step-by-step explanation:

step-by-step explanation:

descending order means to order the polynomials from the term with the largest exponent to the term with the smallest exponent.  

therefore, the correct answer is d.