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

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- Jul 23rd 2007, 03:37 AMDivideBy0Difficult 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 AMtopsquark
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