You have 16 coins that are heads up and 18 coins that are tails up. After you add some coins that are tails up, the ratio of heads up to tails up is 1 to 1.5. How many coins are tails up? How many coins in all?

To find the number of coins that are tails up, we'll first need to determine the number of coins that are heads up.

Given that the ratio of heads up to tails up is 1 to 1.5, we can set up the equation:

(16 + x) / (18 + x) = 1 / 1.5

Where x represents the number of coins added that are tails up.

To solve this equation, we cross-multiply:

1.5 * (16 + x) = 1 * (18 + x)

Expanding both sides of the equation:

24 + 1.5x = 18 + x

Subtracting x from both sides:

0.5x = -6

Dividing both sides by 0.5:

x = -12

Since we can't have a negative number of coins, this would indicate an invalid scenario. It's possible that there was an error in the information provided, as we can't have a negative number of additional coins.

Therefore, without additional information or any possible mistakes, it is not feasible to determine the number of coins that are tails up or the total number of coins.