# In how many ways can you purchase 5 CDs if there are 6 to choose from; 2 cassettes if there are 5 to choose from; and 4 DVDs if there are 4 to choose from?

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### 2 Answers

The number of ways in which 5 CDs can be bought if there are 6 to choose from is given by `C(6, 5) = (6!)/(5!*(6 - 5)!) = 6`

The number of ways of choosing 2 cassettes from a group of 5 is `C(5, 2) = (5!)/(2!*(5 - 2)!) = (5!)/(2!*3!) = 10`

The number of DVDs to be choose from the 4 available is not given. Assuming all the four are bought it can be done in one way.

**The number of ways of buying 5 CDs from the 6 that are available is 6, 2 cassettes can be chosen from the 5 in 10 ways and 4 DVDs can be bought in 1 way if there are 4 to choose from**.

By using the C button on the calculator:

6C5 + 5C2 + 4!

= 6 + 10 + 24

= 40

Please check ans with others as i have just started to learn this topic and am not 100per cent with the ans. i apologise if i am wrong; only trying to help.