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math question

Ren the SAT'erRen the SAT'er Posts: 2,303Registered User Senior Member
edited July 2008 in SAT Preparation
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

  • 33653365 Posts: 602- Member
    its A. i dont know how to explain it.. i can just do it in my head
  • spideyunlimitedspideyunlimited Posts: 976Registered User 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
  • ivyleague104ivyleague104 Posts: 698Registered User 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
    A is your answer

    (BTW if you use this method, you need to make c an integer greater than 1.)
  • arnocarnoc Posts: 324Registered User 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."
  • dchow08dchow08 Posts: 3,267Registered User 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.
  • AjjaredAjjared Posts: 74Registered User 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.
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