中一英數,一題[急](20點)

Let the total number of people be n

Number of people whose blood type is A=40%*n=0.4n
Number of people whose blood type is B=30%*n=0.3n

If there're 30 more people with blood type A than those with blood type B, then:

0.4n-0.3n=30
0.1n=30
n=300

So, Nancy's claim is true for the total number of people to be 300. However, since we do not know the total number of people, to conclude, Nancy's claim is incorrect unless the total number of people is 300.

2010-08-29 19:32:55 補充：
Nancy's claim is correct if the total number of people is 300.

呢題數要有圖先做到嫁bo,
不過,你只要用佢比你既數一個一個over個總數成番100%
睇下你想要果個係幾多%未知囉^^
e.g.
佢比10,20,30你,
你想知10係幾多%,
只要(10/(10+20+30))x100%就得啦,
至於下一條都係咁,
唔明再問啦^^

Yes,I agree with her. Because of the number of people court is unknown so there would be 400 people with blood type A and 300 people with blood type B.As a result, there can be more than 30 people with blood type A than those with blood type B