What is the probability that 4 appear 5 times in the list of numbers 100000 to 999999 inclusive ?
OA [spoiler]53/900000 but not sure [/spoiler]
OA [spoiler]53/900000 but not sure [/spoiler]
Essentially there are 6 digits to be filled with numbers since we are looking at numbers between 1,00,000 and 9,99,999
Assume that we fill all the digits except the first one with 4s in a number _ _ _ _ _ _ then the first digit can be filed in 8 ways,
can not have a 0 or a 4. If we now fix 4s in 1st 3,4,5,6 th place the 2nd can be filled in 9 ways (0 to 9 except 4) this can be
repeated 5 times as we keep moving the place of the 'free' digit (which was 2nd in this case).
Hence numbers possible with 5 4's is = 8 + 9*5 = 53
Total numbers between 1,00,000 and 9,99,999 including 1,00,000 = 9,99,999 - 1,00,000 +1 = 9,00,000
Hence probability = 53/9,00,000
