QR question from topscore

[rockets32]

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This question is on the QR section in Top Score 3 and the way they give to solve the problem is a little confusing at least to me. Here is the question:
How many gallons of pure orange pulp must be added to 30 gallons of a 20% solution of orange pulp to make it a 50% solution?
A 13
B 18
C 22
D 44
E 47

I am sure there is a simple way to solve this but I cant seem to get it. Any help would be appreciated
Thanks!

 

[SF85tea]

The answer is B. 18
(x+ 0.2 *30)/ (x+30) = 50%

x is the gallons of pure orange pulp, add the pulp from 20 gallons of 20% solution divide by the total of (x +30) gallon equals to the new concentration of 50%. hope it helps🙂

 

[tinman831]

This question is on the QR section in Top Score 3 and the way they give to solve the problem is a little confusing at least to me. Here is the question:
How many gallons of pure orange pulp must be added to 30 gallons of a 20% solution of orange pulp to make it a 50% solution?
A 13
B 18
C 22
D 44
E 47

I am sure there is a simple way to solve this but I cant seem to get it. Any help would be appreciated
Thanks!

Here's how I solved it:

A 30 gallon solution (20% of this is pulp) has 6 gallons of total pulp.

6 gallons pulp / 30 total gallons = 20%

You have to add X gallons of pulp to get a %50 percent solution.

6 gallons pulp + X gallons)/ (30 total gallons + X gallons pulp) = .5

.5(30 + X) = (6 + X)

15 +.5X = 6 + X

9 = .5X

X = 18

At least I think thats right.

 

[tinman831]

Darn SF85 beat me to it. At least the answer is right. 😀