Question

A number lock has 3 rings each is marked 0 to 9 in how many ways the lock can't be opened

Answer 1

Each ring is marked 0 to 9:

⇒ There are 10 possible choices

There are 3 rings:

⇒ Total number of possible choices = 10 x 10 x 10 = 1000

Assuming the lock that open be opened with one combination:

⇒ Total number of ways that the lock can't be open = 1000 - 1 = 999

Answer: There are 999 ways that the lock can't be opened.

Answer 2

Given:

3 Rings

0 - 9 Numbered

To find:

The number of ways the padlock cannot be opened.

Solution:

As there are 10 numbers from 0 to 9,

There are 10 possibilities.

10 numbers in all three Rings,

So,

Total number of possibilities = 10^3

Total number of possibilities = 1000

As there is one unlock code for the lock,

The total number of ways that the lock can't be opened = Total number of possibilities -  one unlock code

1000 - 1

The total number of ways that the lock can't be opened = 999 ways.

Hence, there are 999 ways the lock cannot be opened.