Debbie needs to fill juice-cups for her little brother's birthday party. There are 20 juice-cups and each juice-cup holds 10 fluid ounces. The juice comes in 1-gallon bottles. How many 1-gallon bottles of juice will Debbie need to purchase? (1 quart = 32 fluid ounces, 1 gallon = 4 quarts)

Number of juice cups mentioned in question = 20

Quantity of juice that each juice cup can hold = 10 fluid ounces

Quantity of fluid ounces that

20 juice cups require = 20 * 10 fluid ounces

= 200 fluid ounces.

Now

32 fluid ounces = 1 quart

Then

200 fluid ounces = 200/32 quart

= 6.25 quart

Again

4 quart = 1 gallon

So

6.25 quart = 6.25/4 gallon

= 1.56 gallon

So we see that 1.56 gallon of juice is required by Debbie. As the juice comes in 1 gallon bottles, Debbie needs to order 2 bottles of juice.

Debbie will need to buy 2 gallons of juice.