# Math Help - Number of ways

1. ## Number of ways

Suppose you own 30 cassette tapes and 20 cds. If you wish to selct 5 taps and 3 cds to take on a trip with you, in how many ways can you make you selections?

Can anyone explain how to do this for me?
thanks

2. Recall $^{n}C_r = \frac{n!}{r!(n-r)!}$

Cassettes: Choose 5 from 30 $^{30}C_5$

CDs: Choose 3 from 20 $^{20}C_3$

Total: $^{30}C_5+^{20}C_3$

3. Originally Posted by pickslides
Recall $^{n}C_r = \frac{n!}{r!(n-r)!}$

Cassettes: Choose 5 from 30 $^{30}C_5$

CDs: Choose 3 from 20 $^{20}C_3$

Total: $^{30}C_5+^{20}C_3$
so what exactly does the $^{30}C_5+^{20}C_3$ mean

4. $^{30}C_5 = \frac{30!}{5!(30-5)!}$

$^{20}C_3 = \frac{20!}{3!(20-3)!}$

does this help?