# Thread: safes and vault lock combinations qns

1. ## safes and vault lock combinations qns

A safe and vault lock needs to be open.

there are 100 numbers on the dial. ( 0~99 )

The cue is the numbers are whole numbers. (includes zero)

The 3 numbers must be in order to open up the lock
... eg , 40,60,90 not the same as 90 ,60 ,40

Numbers may be repeat,
eg : 20, 20, 80 or 20 80 20 or 20 20 20

In total, how many possible sets of numbers are there ?

Pls show maths workings, and thanks !

2. Originally Posted by thomasleong
A safe and vault lock needs to be open.

there are 100 numbers on the dial. ( 0~99 )

The cue is the numbers are whole numbers. (includes zero)

The 3 numbers must be in order to open up the lock
... eg , 40,60,90 not the same as 90 ,60 ,40

Numbers may be repeat,
eg : 20, 20, 80 or 20 80 20 or 20 20 20

In total, how many possible sets of numbers are there ?

Pls show maths workings, and thanks !
$\displaystyle (100) \cdot (100) \cdot (100) = 100^3$ and the reason should be clear from the answer ....

3. i dont understand ... why 100x100x100 ?

If the numbers are in mutiple of 10s, then = 10x10x10 ?

4. Originally Posted by thomasleong
i dont understand ... why 100x100x100 ?

If the numbers are in mutiple of 10s, then = 10x10x10 ?
Where have you said in your question that the numbers are in multiples of 10's?

5. sorry abt the 10s ... and thanks !

so is 1000 possible combinations ...

This is a true account of one of my friend's mother safes, she forgot her numbers but remember clearly that the numebrs are in 10s ...

Guess she will have to try 1000 times before her safe would open