A beaker contains 500cm^3 solution,of which 40% is starch.
(a)100cm^3 of the solution are drawn and replaced by water.Find the percentage of starch then.
(b)When V cm^3 of the solution are next drawn and replaced by water,the percentage of starch becomes 22.4%.Find V.
Maths problem
2007-03-10 4:27 pm
回答 (1)
2007-03-10 4:37 pm
✔ 最佳答案
Is this your homework? Anyway...a, The % of starch after 100cm^3 of solution are drawn is still 40%
The % of solution is with starch after adding 100cm^3 of water is (400/500)
The % of starch after adding 100cm^3 of water is 40% x (400/500) = 32%
b, Similarly,
32% x (500-V)/500 = 22.4%
32(500-V)/5 = 2240
500-V = 350
V = 150
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