把9L含酒精50%的溶液,稀釋為含酒精30%的溶液,需要加水多少L????
有冇人知!!!THX!!!!!
Maths
2009-09-14 12:09 am
回答 (3)
2009-09-14 7:49 am
✔ 最佳答案
把9L含酒精50%的溶液,稀釋為含酒精30%的溶液,需要加水多少L?酒精 = 9L * 50% = 4.5L
稀釋為含酒精30%的溶液 =>溶液有 4.5L / 30% = 15L
需要加水 15 - 9 = 6L
2009-09-14 12:27 am
=10.5L????
2009-09-14 12:25 am
Original amount of alcohol = 9 x 50% = 4.5L
Original amount of water = 4.5L
Let water to be added = x L
so 4.5/(4.5 + x) = 30%
4.5 = 0.3(4.5 + x)
= 1.35 + 0.3x
0.3x = 3.15
x = 3.15/0.3 = 10.5L = water to be added to get 30% solution.
Original amount of water = 4.5L
Let water to be added = x L
so 4.5/(4.5 + x) = 30%
4.5 = 0.3(4.5 + x)
= 1.35 + 0.3x
0.3x = 3.15
x = 3.15/0.3 = 10.5L = water to be added to get 30% solution.
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