Akey code must contain 6 numbers. there are 10 numbers available. how many different key codes can be created?

The first number in the code can be any one of the 10 available.
           For each of those . . .
The second number in the code can be any one of the remaining 9.
           For each of those . . .
The third number in the code can be any one of the remaining 8.
           For each of those . . .
.
.
The sixth number in the code can be any one of the remaining 5.

The total number of possible codes is  (10 x 9 x 8 x 7 x 6 x 5) =  151,200 .

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.