Question

21. The odd numbers on a regular die are painted red. On a second regular die, the numbers that are one less than a perfect square are painted red. If both dice are thrown, what is the chance that both come up red

Answer 1

The chance that both come up red is 2/3.

Explanation:

First regular die :

The total outcomes are {1,2,3,4,5,6} = 6

Painted red are odd numbers {1,3,5} = 3

Second regular die :

The total outcomes are {1,2,3,4,5,6} = 6

Painted red are one less than perfect square which is 4-1 is {3} = 1

• Probability (both red) = (red in 1st die / total outcome) + (red in 2nd die / total outcome)

P(both red) = 3/6 + 1/6

⇒ 4/6

⇒ 2/3