Question

how many 6- digit telephone numbers can be calculated using the digits 0 to 9 if each numbers starts with 24 and no digit appears more than once?​​

Answer 1

Step-by-step explanation:

Okay! So, number of 6-digit telephone numbers that can be formed if each number starts with 35 and no digit appears more than once -

First and second digits are fixed, i.e.,

1st digit - 3

2nd digit - 5

For 3rd digit, we have 8 choices (1, 2, 4, 6, 7, 8, 9, 0)

For 4th digit, we have 7 choices (because one digit was taken as 3rd digit and repetition is not allowed)

Similarly, we have 6 and 5 choices for 5th and 6th digit.

Here, we will use Fundamental Principle of Multiplication.

The final answer is -

1 * 1 * 8 * 7 * 6 * 5 = 1680

So, there are 1680 such possible numbers.