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# math question

Registered User Posts: 2,303 Senior Member
edited July 2008
the price of ground coffee beans is d dollars for 8 ounces and each ounce makes c cups of brewed coffee. in terms of c and d, what is the dollar cost of the ground coffee beans required to make 1 cup of brewed coffee?

a. d/8c
b. cd/8
c. 8c/d
d. 8d/c
e. 8cd

how do i approach this problem? its always confusing when it has 3 diff things going on =/
Post edited by Ren the SAT'er on

## Replies to: math question

• - Posts: 602 Member
its A. i dont know how to explain it.. i can just do it in my head
• Registered User Posts: 976 Member
1 ounce -> c cups
8 ounces -> 8c cups
d dollars -> 8 ounces -> 8c cups
d dollars -> 8c cups
divide by 8c throughout to get
d/8c dollars -> 1 cup
• Registered User Posts: 698 Member
You can use the the pick numbers method.
Let say 8 dollars buys you 8 ounces, in which each ounce makes 2 cups.
So that costs 1 dollars per ounce, which will make 2 cups.
This is the same as .50 dollars to make 1 cup.
Now plug in 8 for d, and 2 for c, and see which answer gets you .5.
A. (8)/(8x2)= .5

(BTW if you use this method, you need to make c an integer greater than 1.)
• Registered User Posts: 324 Member
Keeping track of units can quickly solve a lot of these problems. You know that dollars has to be in the numerator because your answer is in dollars per cup. This eliminates C. You know that cups has to be in the denominator, again, dollars per cup. This eliminates B and E. Between A and D you need to identify whether you should divide or multiply by 8, and since you have dollars given in "per 8 ounces" you would divide to get dollars "per ounce."
• Registered User Posts: 3,267 Senior Member
Oh these are always confusing.

Let's say it costs 80 dollars for 8 oz. That's 10 dollars for 1 oz. And each ounce makes 5 cups of coffee. So it costs 2 dollars per cup. Clearly I first did 80/8 , and then that divided by 5, which is the same as d/(8c).

It's the same method as Ivyleague's.
• Registered User Posts: 74 Junior Member
these are confusing. i always missed these until a teacher taught me a trick.
It says "d dollars for 8 oz" which is the same as "\$d/8oz."
Next it says 1 ounce = c cups, so
8 ounces = 8c cups
you want cups not ounces so replace 8oz in \$d/8oz with 8c, leaving

d/8c. it's kinda weird method, but it works for me and many people at my school.
This discussion has been closed.