I forgot the last digit of a 7-digit telephone number. If I randomly dial the final 3-digits after dialing the first four, then what is the chance of dialing the correct number? |
$\frac{1}{7!}$ $\frac{1}{100}$ $\frac{1}{729}$ $\frac{1}{1000}$ |
$\frac{1}{1000}$ |
It is given that last three digits are randomly dialed. Then each of the digits can be selected out of 10 digits in 10 ways. Hence required probability = $\frac{1}{1000}$ |