Question

How many no between 1000 to 9900 in which four digits of number are different?

a. 3454

b. 4536

c. 4456

d. 4434?

Answer 1

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Answer 2

Answer:

Option b - 4536

Step-by-step explanation:

To find : How many no between 1000 to 9900 in which four digits of number are different?

Solution :

Since, we have given that the four digits number in which all numbers are different.

The possible ways of placing the number from 0-9 are

In the first place we cannot put 0 because it make 3 digit number.

Number of ways of first number is 9.

In the second place we can put between 0-9 but one number already placed first

So, number of ways of second number is 9.

Similarly, third place has - 8

fourth place is - 7

The best possible ways are:

$9\times 9\times 8\times 7=4536$

Therefore, Option b is correct.