从一瓶浓度为20%的消毒液中倒出2/5后,加满清水,再倒出2/5,又加满清水,此时消毒 夜的浓度为( )
2023-06-09
A.7.2%
B.3.2%
C.5.0%
D.4.8%
参考答案:A
B.3.2%
C.5.0%
D.4.8%
参考答案:A
每一次稀释,溶质的量都变为原来的1-2/5=3/5,而溶液的量不变,则浓度也变为原来的3/5, 因此最后的浓度为20%×3/5×3/5=7.2%
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