Question

Lila's retirement party will cost $8 if she invites 4 guests. If there are 9 guests, how much will Lila's retirement party cost? Solve using unit rates.

Answer 1

We are assuming that the party cost is directly proportional to the number of guests.

Then, if it will cost $8 for 4 guests, the unit rate is:

$c=\frac{8\text{ dollars}}{4\text{ guests}}=2\text{ dollars per guest}$

Then, we can use this unit rate to calculate the cost for 9 guests:

$C(9)=2\frac{\text{ dollars}}{\text{ guest}}\cdot9\text{ guests}=18\text{ dollars}$

The cost for 9 guests is $18.