Answer to Question #300474 in Algebra for kilee

Question

A cookie recipe for 60 cookies calls for 4 cups of flour. How much flour is needed to make 90 cookies?

Answer 1

Let x be the number of cookies we get for 1 cup of flour. Then,

$\begin{array}{|c|c|} \hline \text{Number of cup of flour}& \text{Number of cookies}\\ \hline 4&60\\ 1&x\\ \hline \end{array}\\$

$\therefore x = \dfrac{60}{4}=15$ i.e., 1 cup of flour makes 15 cookies.

Let y be the number of cups of flour required to make 90 cookies.

$\begin{array}{|c|c|} \hline \text{Number of cup of flour}& \text{Number of cookies}\\ \hline 1&15\\ y&90\\ \hline \end{array}\\$

$i.e., 15y = 90\Rightarrow y = \dfrac{90}{15}=6$. Hence we require 6cups of flour to make 90 cookies.