Math一問~~~~~
2007-02-11 3:36 am
There are some VCDs , DVDs and CDs on a shelf . The number of VCDs is 10 more than that of DVDs , and 4 less than that of CDs . If a disc is selected at random , the probability of selecting a VCD is 10/27 . Find the number of VCDs on the shelf .
回答 (1)
2007-02-11 3:41 am
✔ 最佳答案
let the number of DCDs on the shelf is x .Then The number of VCDs is x+10
The number of CDs is x+10+4=x+14
a disc is selected at random , the probability of selecting a VCD is 10/27
So
(x+10)/(x+x+10+x+14)=10/27
(x+10)/(3x+24)=10/27
30x+240=27x+270
3x=30
x=10
the number of VCDs on the shelf is 20
收錄日期: 2021-04-25 16:54:14
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