Phoebe eats 1 serving and gives her dog 1 serving of peanut butter for a bedtime snack. Each jar of peanut butter has 15 servings.  How many jars will she need to make sure she and her dog have enough to last for 30 days?
##Solution## She and her dog both have a serving before bed so they eat 1+1 = <<1+1=2>>2 servings a day
She wants to have enough for 30 days and they eat 2 servings a day so they need 30*2 = <<30*2=60>>60 servings
Each jar has 15 servings and she needs 60 servings so she will need 60/15 = <<60/15=4>>4 jars of peanut butter
#### 4