標題: = =%%.. [打印本頁] 作者: 啦啦啦 時間: 1/10/2007 02:43 PM 標題: = =%%.. alcohol and water are mixed in the ratio of 4:1 in volume. if 15% of alcohol is evaporated,and
an additional 30% of the original amount of water is added ,
what is the ratio of alcoholl of water in the final mixture ?
要let 數,,點做=0= ..作者: abc666 時間: 1/10/2007 03:03 PM let the total initial volume of mixture be 100cm3 final volume of alcohol =80 X (1-15%) =68cm3 final volume of water =20X(1+30%) =26cm3
final ratio of volume of alcohol to water =68:26 =34:13
PS. I found that I can never remember how to spell 'alcohol'~.~
[ 本帖最後由 abc666 於 1/10/2007 03:06 PM 編輯 ]作者: Royal 時間: 1/10/2007 04:44 PM Let the original volume of this mixture be X --> the original volume of alcohol is 4/5 X --> the original volume of water is 1/5 X
As 15% of alcohol is evaporated, there are only (100%-15%)(4/5 X) of alcohol remains. Also, (1/5 X)(30%) of water is added, thus there is (1/5 X)(100%+30%) of water in the mixture.
Alcohol remained =(100%-15%)(4/5 X) = 0.85 (4/5 X) = 0.68 X
Water remained = (100%+30%)(1/5 X) = 1.3 (1/5X) = 0.26 X
So, the ratio of alcohol of water = 0.68 X / 0.26 X = 34 / 13