hey guys, can anyone help me to sort this out ?
12) (4 marks) How many litres of a 5% solution (by volume) must be
added to a 10% solution to obtain 20 litres of an 8% solution?
pls show the answer in details ! thanks a lot people.
a maths question to ask please?
2011-12-11 11:19 am
回答 (4)
2011-12-11 11:23 am
✔ 最佳答案
5V + 10(20 -- V) = 8*20 gives V = 20(10 -- 8) / (10 -- 5) = 88 L 5% solution mixed with 12 L 10% solution will give 20 L 8% solution ANSWER
2011-12-11 7:40 pm
Let x be the number of liters of 5% solution and y be the number of liters of 10% solution.
1) x + y = 20 or y = 20 - x
2) 0.05x + 0.10y = 0.08(20)
substitute eq(1) into eq(2):
0.05x + 0.10(20 - x) = 1.6
0.05x + 2 - 0.10x = 1.6
-0.05x = -0.4
x = -0.4/-0.05 = 8 liters
using eq(1):
y = 20 - 8 = 12 liters
check using eq(2):
0.05(8) + 0.10(12) = 0.08(20)
0.4 + 1.2 = 1.6
8 liters of 5% solution and 12 liters of 10% solution will make 20 liters of 8% solution.
- .--
1) x + y = 20 or y = 20 - x
2) 0.05x + 0.10y = 0.08(20)
substitute eq(1) into eq(2):
0.05x + 0.10(20 - x) = 1.6
0.05x + 2 - 0.10x = 1.6
-0.05x = -0.4
x = -0.4/-0.05 = 8 liters
using eq(1):
y = 20 - 8 = 12 liters
check using eq(2):
0.05(8) + 0.10(12) = 0.08(20)
0.4 + 1.2 = 1.6
8 liters of 5% solution and 12 liters of 10% solution will make 20 liters of 8% solution.
- .--
2011-12-11 7:24 pm
Vol of 5% =x
Vol of 10% =y
x+y =20
5x + 10y= 8(x+y)
x=8
y=12
Vol of 10% =y
x+y =20
5x + 10y= 8(x+y)
x=8
y=12
2011-12-11 7:22 pm
2.5% / 5% / 1.25% / 2.5% / 0.625% / 1.25%
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