數學不識 ?????

there are 1white ,4green and 5 red balls in a bag.. two balls are drawn
at random with replacement.what is the probability that
i)both are
red?
P(both red)
= [5/(1+4+5)]^2
= (5/10)^2
= 1/4
ii)both are of the same colour?
P(both same colour)
= (5/10)^2 + (1/10)^2 + (4/10)^2
= (25+1+16)/100
= 42/100
= 21/50
iii)they are different in
colour
P(different colour)
= 1- 21/50
= 29/50
2.the probability that a man will be alive in 25 years is 0.8 and the
probability
that his wife will be alive in 25 years is 0.85. find the
probability that
i)both will be alive in 25years
P(both will be alive in 25years)
= 0.8 * 0.85
= 0.68
ii)only the man
will be alive in 25 years
P(only the man
will be alive in 25 years)
= 0.8 * (1-0.85)
= 0.12
iii)at least one will be alive in 25 years

P(at least one will be alive in 25 years)
= 0.12 + 0.68 + (1-0.8)*0.85
= 0.12 + 0.68 + 0.17
= 0.97

ｗｈａｔ　ｉｓ　ｗｈｒｉｔｅ？

?? white?

1 white???!