A gardener has 26 lb. of a mixture of fertilizer and weed killer. If 1 lb. of the mixture is replaced by weed killer, the result is 5% weed killer. What % of the original mixture was the weed killer?
The original mixture was
So, you know that you have mixture containing weed killer, let's say
Moreover, you know that this mixture has a mass of 26 pountds. Now, you remove one pound from the original mixture and add one pound of weed killer.
Your mixture is now
Now, to get the mass of the weed killer in the original mixture, simply subtract the added 1 lb.
SInce the mass of the mixture is unchanged, the original percent concentration of the mixture was