There are 40 people at a reception for international students. The students, boys and girls, are from Peru and China. 18 of all the students are boys, and 12 of all the students are Peruvian. 7 of the Peruvians are girls. Given that a student is a boy, what is the probability that he is Chinese? A Venn diagram will help you to answer this question.

Question

anonymous · Answer

@phi

anonymous · Answer

@amistre64

phi · Answer

did you try to draw a Venn diagram ?

anonymous · Answer

no. can u help me start? im sorry probability really confuses me

phi · Answer

|dw:1375228906313:dw|

anonymous · Answer

plus I can oly spend 5 mins on this problem

phi · Answer

7 of the Peruvians are girls.

fill in the correct box

phi · Answer

there are 4 boxes  or slots.  7 goes into the slot labeled Peru and girls

phi · Answer

next
12 of all the students are Peruvian.

if 7 are girls, that means the 5 remaining are boys

put 5 into the slot:  boys and Peru

phi · Answer

18 of all the students are boys,

if 5 boys are from Peru, that means the rest are from China

13 boys are from China.  Put 13 in the slot:  boys and China

anonymous · Answer

what is this supposed to look like... 3 different ones right?...

phi · Answer

Given that a student is a boy, what is the probability that he is Chinese?

count the number of boys:  18

count the number of Chinese boys: 13
take the ratio

anonymous · Answer

ohh so...

phi · Answer

Good luck.  I don't like doing tests for other people.

anonymous · Answer

its not a test

anonymous · Answer

so its 13/18?

anonymous · Answer

13/18 ?

anonymous · Answer

wait no 5/18 I mean?