if 30% of a solution equals 5L, how many L of water do you add to make it 20% of the solution?
回答 (2)
2010-06-15 4:19 pm
✔ 最佳答案
30% of 5L = 1.5 L20% of X = 1.5L
X = 1.5 / 0.2 = 7.5 L
so you have to add (7.5–5) = 2.5 Liters.
.
2010-06-16 12:29 am
Let the volume of water be x.
active ingredient / volume = concentration
active ingredient = 30% * 5
volume = 5 + x
(30% * 5) / (5 + x) = 20%
1.5 / (5 + x) = 0.2
1.5 / (5 + x) * (5 + x) = 0.2 * (5 + x)
1.5 = 1 + 0.2x
0.2x = 0.5
x = 2.5
active ingredient / volume = concentration
active ingredient = 30% * 5
volume = 5 + x
(30% * 5) / (5 + x) = 20%
1.5 / (5 + x) = 0.2
1.5 / (5 + x) * (5 + x) = 0.2 * (5 + x)
1.5 = 1 + 0.2x
0.2x = 0.5
x = 2.5
收錄日期: 2021-05-01 13:15:31
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100615081618AAcLAdL