Question 183490
Let {{{a}}}= ounces of the 15% solution needed
Let {{{b}}}= ounces of the 17% solution which will result
given:
(1) {{{a + 4 = b}}}
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(2) {{{.15a + .2*4 = .17b}}}
I have 2 equations and 2 unknowns, so it's solvable
Multiply both sides of (1) by {{{.15}}} and subtract
from (2)
(2) {{{.15a + .2*4 = .17b}}}
(1) {{{-.15a - .15*4 = -.15b}}}
(3) {{{.05*4 = .02b}}}
{{{.02b = .2}}}
{{{b = 10}}}
Plug this value back into (1)
(1) {{{a + 4 = b}}}
(1) {{{a + 4 = 10}}}
(1) {{{a = 6}}}
6 ounces of the 15% solution must be mixed with
4 ounces of the 20% solution to make 10 ounces
of the 17% solution
check answer:
(2) {{{.15a + .2*4 = .17b}}}
(2) {{{.15*6 + .2*4 = .17*10}}}
(2) {{{.9 + .8 = 1.7}}}
(2) {{{1.7 = 1.7}}}
OK