A person going to a party was asked to bring 4 different bags of chips. Going to the store, she finds 13 varieties. How many different selections can she make?
(this is a probability question)

Step-by-step explanation:

13!/4(13-4)!

13!/4(9)!

Continue simplifying.

The formula for combinations n!/r!(n-r)! pay attention to class next time

54 km / hours

step-by-step explanation:

we need to convert seconds to hours

60 seconds = 1 minutes

60 minutes = 1hour

15 m         60 second   60 minutes

  * *         = 54000 meters/ hour

second     1 minute             1 hour

now we need to convert meters to km

1000 m = 1 km

54000 m       1 km

*   = 54 km / hours

hour               1000m

take the logarithm of both sides (the base of the log doesn't matter):

apply the exponent property - this says that :

distribute the log terms on both sides:

group like terms together:

divide through both sides by the coefficient on :

you can do some additional rewriting here using the properties of the logarithm to simplify things if you like: