DAY 80

Comment

This item involves conditional probability, but it can be solved without calculating specific probabilities.
If Ted starts with plate A, then his choice from B would be from either 2 blue and 4 white, or 3 blue and 3 white pills.
If he starts with plate B, then his choice from A would be from ... .

Answer

It is better to start with plate B.

Readers' methods

P Scales, Norfolk:
If he starts with A, his chances of picking a blue pill will be evens or worse.
If he starts with B, his chances of picking a blue pill will be evens or better.
So he should start with B.

JMG, Bath BA2:
If starting with A: P(Blue) = (2 + 3/5)/6 = 13/30
If starting with B: P(Blue) = (3 + 2/5)/6 = 17/30
17/30 > 13/30 therefore starting with B has a better chance of getting blue.

T Edwards, Hertfordshire SG12:
If Ted takes a pill from plate B, then plate A has either
3 blue + 3 white or
4 blue + 2 white.
then Probability of choosing blue, P = 3/6 or 4/6.
If he takes a pill from plate A, then plate B has either
2 blue + 4 white or
3 blue + 3 white.
Then P = 2/6 or 3/6 that a blue pill is chosen.
So the best chance of obtaining a blue pill starts at plate B.