Question 752538
there is now 10kg of rye, this will not chankge.  we want to add x kg of wheat to the 100kg of mixed grains we have, so that 4% (4/100) of it will be 10kg of rye

4/100 * (100 +x) = 10
multiply out and reaarange to get 4x=600
x = 150

so we need to add 150kg of wheat 

(this gives us 250kg of mixture of which 4% is rye, because 10kg/250kg is 4%)