PP-T1-PS 8

[王炯棻]

8. 1221-!-item-!-187;#058&000650
A flower arrangement consists of 30 roses, each of which is either white or red. If a rose is to be selected at random from the flower arrangement, the probability that the rose selected will be white is twice the probability that it will be red. How many white roses are in the flower arrangement?

(A) 5
(B) 10
(C) 15
(D) 20
(E) 25

ANS:D

[王炯棻]

請問這題怎麼算呀～～～～謝謝囉

[Huang Hsin-Yi]

w/30=2*R/30
w+R=30

[chiungfen]

謝謝妳的回覆呦~~