pushpitkc wrote:

A palindrome is a number that reads the same forward and backward. For example - 1331.

How many 4-digit palindromes can be formed using two of the five digits - 1,3,5,7, and 9?

A. 10

B. 20

C. 30

D. 40

E. 60

Source:

Experts GlobalHow many 4-digit palindromes can be formed

using two of the five digits - 1,3,5,7, and 9?

This means that the digits can not be repeated.

4 digit no looks like: _ _ _ _

We will start filling from the Thousands place.

Thousand's place can be filled in 5 ways.

Hundred's place can be filled in 4 ways.

Tenth's place has to be the same as hundreds place, so it can be filled in only 1 way.

One's Place has to be the same as hundreds place, so it can be filled in only 1 way.

Hence, 5x4x1x1= 20 ways.

My answer: B
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~R.

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