30061989 wrote:

The digits 5,6,7,8 can be arranged without repetition to form the no. 7685. According to the given data,find the position of 7685 if the 4-digit numbers formed using the given digits are arranged from the start in ascending order and from the end in descending order of magnitude?

Answer: Position of 7685 from start in ascending order = 16

Position of 7685 from end in descending order=9

Hi...

1) in ascending order..

Before the thousands digit becomes 7, it can take 5 and 6..

a) With 5 in thousands digit, 5_ _ _, rest three digits 6,7 and 8 can be arranged in 3!=6 ways..

b) Similarly with 6 as thousands digit, 6 _ _ _, 3! Or 6 numbers can be formed..

c) Now with 7 as thousands digit, 5 can be in hundreds digit, 75_ _and remaining 2 in 2! Ways..

With 7 in thousands, and 6 in hundreds.....7658 is one possibility

After that is the number required 7685..

So the position is 6+6+2+1+1=16..

2) in descending order..

Total all ways 4!=24..

So if 16 in ascending order, 24-16+1 in descending order..

Ans 9

OR..

We can find in the similar way as (1) above

Hope it helps

_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372

Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html