Thread: [SOLVED] SAT math page 718 #8

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) $\displaystyle \frac{d}{8c}$

b)$\displaystyle \frac{cd}8$

c)$\displaystyle \frac{8c}{d}$

d)$\displaystyle \frac{8d}{c}$

e) 8cd

I think its because because: if you have d dollars for 8 ounces. Then 1 ounce would be $\displaystyle \frac{15}{8}$ And if ONE ounce is needed to make 1 cup of brewed coffee so then $\displaystyle \frac{cd}{8}$

but why is the correct answer $\displaystyle \frac{d}{8c}$??

Thanks in advance

I answered this very same question here: http://www.mathhelpforum.com/math-he...onversion.html

Shortcuts!!

There is no need to convert units here. Follow me carefully:

8 ounces = d dollars ... (1)
1 ounce = c cups ...(2)

Therefore,

8 ounces = 8c cups ... (3) = multiply eq(2) by 8

Therefore again,

d dollars = 8c cups .. (3) and (1)

switch side for clarity:

8c cups = d dollars

1 cup = d/8c dollars (Answer)

Got it?