Blue -- B --- 3
Navy -- N -- 5
Turquoise -- T -- 2
a) his choices could be BN, BT, OR NT
prob(Blue Navy) = C(3,1) C(5,1)/C(10,2) = 3*5/45 = 1/3
prob(B T) = C(3,1) C(2,1)/C(10,2) = 6/45 = 2/15
prob(N T) = ...
add them up
or
Prob(B N) = (3/10) (5/9) (2) , times 2 because it could be BN or NB
= 30/90 = 1/3
etc for the other two
b) 3 of the same colour, implies it can only be BBB or NNN
combination way:
prob(BBB) = C(3,3)/C(10,3) = 1/120
other way:
prob(BBB) = (3/10)(2/9)(1/8) = 6/720 = 1/120
find NNN in the same way, then add them up
1. Papa Tom Smurf is a smurf-player. He wants to take two smurfettes out on a date. There are 3 blue smurfettes, 5 navy smurfettes and 2 turquoise smurfettes.
a) What’s the probability that the smurfettes he dates are of different colours? (4)
b) If he instead takes three smurfettes out on a date, what’s the probability that they are all of the same colour? (3)
I am extremely confused with probability, can someone please help?
1 answer
1 answer