Kevin has an equal number of quarters nickels and dimes in his piggy bank, he randomly picks a coin replaces it and picks another coin. What is the probability that the sum of the two coins picked is at least thirty cents

P(q) = 1/3

P(n|d,q) = 2/9
P(n|d,n|d) = 4/9

So, what do you think?

the 1st probability means that if the 1st coin is a quarter, the 2nd does not matter.

q q *

- n *
- d *

n q *
- n :(
- d :(

d q *
- n :(
- d :(
so
5/9

100./.

I think it is A or D

To find the probability that the sum of the two coins picked is at least thirty cents, we need to calculate the favorable outcomes (the number of ways the sum can be at least thirty cents) and divide it by the total possible outcomes.

Let's break it down step by step:

Step 1: Determine the total possibilities:
Since Kevin has an equal number of quarters, nickels, and dimes, we need to find the total number of coins in the piggy bank. Let's assume he has "x" quarters, "x" nickels, and "x" dimes. Therefore, the total number of coins is 3x.

Step 2: Calculate the favorable outcomes:
To find the favorable outcomes, we need to consider all the possibilities where the sum of the two coins picked is at least thirty cents. We can break down this into three cases:

Case 1: Both coins chosen are quarters:
The value of each quarter is 25 cents, and he has "x" quarters. So, the number of favorable outcomes in this case is x.

Case 2: One coin chosen is a quarter and the other coin is a dime:
The sum of a quarter and a dime is 35 cents. He has "x" quarters and "x" dimes. Therefore, the number of favorable outcomes in this case is x * x.

Case 3: One coin chosen is a quarter and the other coin is a nickel:
The sum of a quarter and a nickel is 30 cents. He has "x" quarters and "x" nickels. Therefore, the number of favorable outcomes in this case is x * x.

Step 3: Add up the favorable outcomes:
Add up the favorable outcomes from the three cases: x + x * x + x * x = x + x^2 + x^2 = x^2 + x + x^2 = 2x^2 + x.

Step 4: Calculate the probability:
To find the probability, divide the favorable outcomes by the total possibilities. The probability is the number of favorable outcomes divided by the total number of coins, which is 2x^2 + x divided by 3x.

So, the probability that the sum of the two coins picked is at least thirty cents is:

(2x^2 + x) / (3x).

Please note that this is a general solution based on the given information about Kevin's piggy bank. The specific value of x, which represents the number of each type of coin, would need to be known to calculate the probability exactly.