Math:system of equations

Question

Emmanuel is a chef he is going to make a make sure using two brands of Italian dressing the first spring contains 9% vinegar and the second brand contains 40% vinegar Manuel wants to 240 mL of a dressing that is 13% vinegar

Answer 1

Let F = mL of 40%, N= mL of 90%

40F + 9N = 240(13) = 3120

40F + 9(240-F) = 3120

40F-9F = 3120 - 2160 = 960

31F = 960

F = 960/31 = 30.97 mL of 40%

240-F = 209.03 mL of 9%

40 is within 27 of 13

9 is within 4 of 13

you need 27/4 times as much 9 as 40%

N/(240-N) = 27/4

4N = 6480-27N

31N = 6480

N = 6480/31 = 209.03 mL of 9%

240-N = 30.97 of 40%

it's about 31 mL of 40% mixed with 209 mL of 9% to yield 240 mL of 13%