Given data,
fertilizer blend (b1) = 40 percent nitrogen and 60 percent potassium by weight.
different blend (b2) = 20 percent nitrogen and 80 percent phosphorus
Given condition, above mixtures blends are combined to create a final mixture, the result = 35 percent nitrogen.
final mixture weighs (b1 + b2) = 24 kilograms
we have to find, how many kilograms of phosphorus ?
From above, we can conclude that, b1 + b2 = 24 ---> equation 1
and as per nitrogen percent in final mixture, (40/100)b1 + (20/100)b2 = (35/100)(24) => 0.4b1 + 0.2b2 = 8.4 ---> equation 2
From equation 1 and equation 2, lets solve for amount of 2nd blend i.e., different blend used in final mixture (as it contains both nitrogen and phosphorous)
b1 + b2 = 24 x(0.4) => 0.4 b1 + 0.4 b2 = 9.6
0.4b1 + 0.2b2 = 8.4 => 0.4 b1 + 0.2 b2 = 8.4 , Lets find difference now
cancelling b1, we have 0.2b2 = 1.2 => b2 = 6
as per given data, b2 mixture contains 80 percent phosphorus
final mixture contains phosphorus of (80/100)6 = 4.8 kgs