probability

Question

A spinner has 10
equally sized sections,
 2 of which are gray 8 and
of which are blue. The spinner is spun twice. What is the probability that the first spin lands on blue and the second spin lands on gray ?
Write your answer as a fraction in simplest form.

Answer 1

P( Blue on 1 AND Gray on 2)   Remember that AND means multiply...

 

P(Blue on 1) * P(Gray on 2)

 

(8/10) *  (2/10)  = 16/100 = 4/25

 

 

See if these probabilities make sense.  Notice that all the possible combinations are listed below and the entire thing adds up to 1 or 100%.

 

P(Gray, Gray) = .2(.2) = .04

P(Gray, Blue) = .2(.8) = .16

P(Blue, Blue) = .8(.8) = .64

P(Blue, Gray) = .8(.2) = .16