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

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

Step-by-step 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