Seed mixture X is 40 percent ryegrass and 60 percent bluegrass by weight; seed mixture Y is 25 percent ryegrass and 75 % fescue. If a mixture of X and Y contains 30% ryegrass, what percent of the weight of the mixture is X?
B. 33 1/3%
E. 66 2/3%
In this my approach was that let weight of X be 100 and weight of Y be 100
Now For X, ryegrass is 40% of 100=40
and for total mixture it will be 30%of 200=60
To calculate the percentage weight from mixture X
why it is wrong 40/60 *100
Your first assumption is incorrect here: In this my approach was that let weight of X be 100 and weight of Y be 100
If you are assuming that the weights are 100 each and the combined weight is 200, what is left to find? X would be 1/2 of the mixture 100/200. What you have to find is the ratio of the weights in which they were mixed. The ratio may not be 1:1 as you have assumed here.
X has 40% ryegrass and Y has 25% ryegrass. Total mix has 30% ryegrass.
So X/Y = (25 - 30)/(30 - 40) = 1/2
So X by weight is 1 part (say 100 gms) and Y is 2 parts (say 200 gms). So X is 1/3 of the total mix i.e. 33.33%
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