Question

Find the average number of numbers formed by the numbers 1, 2, 3, 4 without using the number in the corner more than once.​

Answer 1

ANSWER

Step-by-step explanation:

Given digits 1,2,3,4,3,2,1

We needed 7 digit number, which is same as filling 7 places in a row with the 7 digits 1,2,3,4,3,2,1

Odd places are to be filled by 1,3,5,7 digits.

Odd digits are available 1,3,3,1

i.e. two is 1

′

s and two. 3

′

s.

4 odd digit can be arranged at 4 odd places in

2!2!

4

P

4

=6 ways.

Now there are 3 even places.

Required such number =

2!

3!

Now using fundamental Law of multiplication.

Total number of ways are 6×3=18