# Difficult mixing ingredients

• Jul 23rd 2007, 03:37 AM
DivideBy0
Difficult mixing ingredients
I have 450 grams of salt and flour mix. How many grams of flour should I add to reduce the percentage of salt in the mixture to 90% of what it was?

(a) 50
(b) 10
(c) 30
(d) 45
(e) 60
• Jul 23rd 2007, 04:47 AM
topsquark
Quote:

Originally Posted by DivideBy0
I have 450 grams of salt and flour mix. How many grams of flour should I add to reduce the percentage of salt in the mixture to 90% of what it was?

(a) 50
(b) 10
(c) 30
(d) 45
(e) 60

You want to add x grams of flour to the 450 grams of salt. Thus you will have a total mass of 450 + x grams. This will make the amount of salt be 90% of the total so:
$\displaystyle \frac{450}{450 + x} = \frac{90}{100}$ <-- Cross multiply

$\displaystyle (450)(100) = (90)(450 + x)$

$\displaystyle 45000 = 40500 + 90x$

$\displaystyle 45000 - 40500 = 90x$

$\displaystyle 4500 = 90x$

$\displaystyle \frac{4500}{90} = x$

$\displaystyle x = 50$

So we need to add 50 grams of flour.

-Dan