Question

Each morning Soriano buys coffee and donut holes for his employees and clients. The following system represents the amount of coffee and donut holes bought this morning and the amount of money that he spent (in dollars). In the system, represents the number of cups of coffee that he bought and the number of cups of donut holes that he bought.

c+d=60

2.5+1.75=123.75

Part A: How many cups of coffee and donut holes did Soriano buy this morning?

Part B: How much does each cup of coffee cost?

Part C: How much does each cup of donut holes cost?

Part D: How much did Soriano spend in coffee and donut holes?

Part E: Use the elimination method to solve the system and determine the number of cups of coffee and donut holes that Soriano bought this morning.

Answer 1

Part A: 60

Part B: Each cup of coffee costs 2.5 dollars

Part C: Each donut costs 1.75 dollars

Part D: Sonario spent 123.75 dollars in coffee and donut holes

Part E: The number of cups of coffee bought are 25 cups of coffee

The number of donut holes bought are 35 donut holes

Explanation:

The given parameters are;

c + d = 60

2.5 × c + 1.75 × d = 123.75

Part A

Whereby the number of cups of coffee bought = c, and the number of donut holes bought = d, then, the total number of cups of coffee and donuts bought is c + d = 60

Part B:

From the second equation for the total cost of cups of coffee and holes of donuts, the coefficient multiplying the variable representing an item is the cost of the item

Therefore, each cup of coffee costs 2.5 dollars

Part C:

Using the method from above, each donut costs 1.75 dollars

Part D:

From the equation for the total cost, Sonario spent 123.75 dollars in coffee and donut holes

Part E:

By the elimination method, we have;

c + d = 60

∴ c = 60 - d

Eliminating c in the equation for the total cost gives;

2.5 × c + 1.75 × d = 2.5 × (60 - d) + 1.75 × d = 123.75

150 - 2.5·d + 1.75·d = 150 - 0.75·d = 123.75

150 - 123.75 = 0.75·d

26.25 = 0.75·d

d = 26.25/0.78 = 35

d = 35

c = 60 - d = 60 - 35 = 25

c = 25

∴ c = The number of cups of coffee bought = 25 cups of coffee

d = The number of donut holes bought = 35 donut holes