數學問題＜＜急！！！(probability)

這條題目簡意是在抽屜5條的巾中取出一條，再放回去，然後再取出一次。

(A)Find the probability that both scarves taken are the same scarf.

第一次取出任何一條是1/5機會，第二次又要相同就會是1/5x1/5=1/25。
但是不要忘記，這會出現五次，所以將1/25x5=1/5//
如果寫作式去回答就是：

[P(1)xP(2)]x5
=(1/5x1/5)x5
=1/5//

(B) Find the probability that both scarves taken are in the same colour.

這是問兩次都抽到同色。所以要分開來看。
第一次抽到紅色的機會是2/5，第二次又抽到的機會便會是2/5X2/5=4/25。
第一次抽到白色的機會是3/5，第二次就會是3/5X3/5=9/25。
所以，將兩種可能性加起來，便會是答案：4/25+9/25=13/25。
用式寫出來就會是：

P(1)+P(2)
=(2/5x2/5)+(3/5x3/5)
=4/25+9/25
=13/25//

(a)
the probability that both scarves taken are the same scarf
=(1)[1/(2+3)]
=1/5
(1) represents taking a scarf in the first time , as in the first time you can take any scarf .therefore , the probability is 1
On the second time ,you have to take the scarf taken in the first time and the scarf is the only one out of 5 .Thus , the probability is 1/5
(b)
the probability that both scarves taken are in the same colour
=the probability that both are red or the probability that both are white
=(2/5)(2/5)+(3/5)(3/5)
=(4/25)+(9/25)
=13/25