The number of five-digit numbers that contain 7 exactly once is a. `(41)(9^3)` b. `(37)(9^3)` c. `(7)(9^4)` d. `(41)(9^4)`

Find the number of n digit numbers, which contain the digits 2 and 7, but not the digits 0, 1, 8, 9.

The number of planes that are equidistant from four non-coplanar points is a. 3 b. 4 c. 7 d. 9

A die is thrown a fixed number of times. If probability of getting even number 3 times is same as the probability of getting even number 4 times, then probability of getting even number exactly once is a. 1//6 b. 1//9 c. 5//36 d. 7//128

The total number of five-digit numbers of different digits in which the digit in the middle is the largest is a. sum_(n=4)^9^n P_4 b. 33(3!) c. 30(3!) d. none of these

The number of five-digit numbers which are divisible by 3 that can be formed by using the digits 1,2,3,4,5,6,7,8 and 9 , when repetition of digits is allowed, is

The number of four-digit numbers that can be formed by using the digits 1,2,3,4,5,6,7,8 and 9 such that the least digit used is 4 , when repetition of digits is allowed is

The number 916238457 is an example of a nine-digit number which contains each of the digit 1 to 9 exactly once. It also has the property that the digits 1 to 5 occur in their natural order, while the digits 1 to 6 do not. Find the number of such numbers.