求一道数学jj解答

iaboutyou

玩具80%在亚洲，25%在欧洲，问只在亚洲的多少概率
1，即欧洲又在亚洲的是25%
2，既不是欧洲也不是亚洲的是15%

理解不了
谢谢！

sdcar2010

Category: Asia only  Europe Only  Both A & E  Neither A nor E
                a             b                    c                 d
a+b+c+d = 100
a+c = 85
b+c = 25

What is a?  
4 unknowns, 3 equations. We need one more independent equation

condition 1) c= 25. Then a = 85-25 = 60. Sufficient.

condition 2) d= 15. Then a+b+c = 85. Then a =85-25=60. Sufficient.

Since both are sufficient, DDDDDDDDDDDDDDDDDD

iaboutyou

got it
ThXXXXXXXXXX

Category: Asia only  Europe Only  Both A & E  Neither A nor E
                a             b                    c                 d
a+b+c+d = 100
a+c = 85
b+c = 25

What is a?  
4 unknowns, 3 equations. We need one more independent equation

condition 1) c= 25. Then a = 85-25 = 60. Sufficient.

condition 2) d= 15. Then a+b+c = 85. Then a =85-25=60. Sufficient.

Since both are sufficient, DDDDDDDDDDDDDDDDDD

-- by 会员 sdcar2010 (2011/12/11 1:05:51)