Question 1164523: For a segment of a radio show, a disc jockey can play 10 records. If there are 12 records to select from, in how many ways can the program for this segment be arranged?
Answer by ikleyn(52802)   (Show Source):
You can put this solution on YOUR website! .
In 12*11*10*9*8*7*6*5*4*3 = 239500800 ways.
It is the product of 10 consecutive integer numbers, starting from 12 in descending order.
1-st record to play can be any one of 12 records;
2-nd record to play can be any one of remaining 11 records;
3-rd record to play can be any one of remaining 10 records;
4-th record to play can be any one of remaining 9 records;
. . . and so on . . .
The last, 10-th record to play can be any one of remaining 3 records.
The product of these numbers, from 12 to 3, gives the answer.
Solved.
This mantra is the standard method solving such problems.
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