# Probability of 2 independent variables

#### poisonroxs

##### New member
Is this correct?

A certain airplane has two independent alternators to provide elecrical power. The probability that a given alternator will fail on a 1 hour flight is .02. What is the probability that

a) both will fail?
b) neither will fail?
C) One or the other will fail?

A) P(x=2) .02*.02= .0004 or 4%

B) P(x=0) 1-0.02=.98
(.98*.98)= .09604 or 9.6%

C) P(x=1) 2(.98)(.02)=.0392 or 3.9%

Thanks for any input in advance )

#### Subhotosh Khan

##### Super Moderator
Staff member
poisonroxs said:
Is this correct?

A certain airplane has two independent alternators to provide elecrical power. The probability that a given alternator will fail on a 1 hour flight is .02. What is the probability that

a) both will fail?
b) neither will fail?
C) One or the other will fail?

A) P(x=2) .02*.02= .0004 or 0.04%

B) P(x=0) 1-0.02=.98
(.98*.98)= 0.9604 or 96%

C) P(x=1) 2(.98)(.02)=.0392 or 3.9%

Thanks for any input in advance )

#### poisonroxs

##### New member
Sorry but I do not understand your post. What do the red marks mean, are they incorrect?

#### stapel

##### Super Moderator
Staff member
poisonroxs said:
What do the red marks mean, are they incorrect?
Compare what you'd posted with what the tutor posted; in particular, compare the tutor's red-highlighed text with your corresponding black text. While doing so, recall that the total of the probabilities, since they cover all possible cases, should add up to 100%. What total do your values give? What total do the tutor's values give? :wink:

Eliz.

#### poisonroxs

##### New member
so this is how I should present my answer?
A) .0004
B) .9604
C) .0392
this all added together equals 1

Thank you in advance