MATH 157
posted by Rayna on .
Can anyone please help me understand these math problems.
#4. How many threesymbol codes (letternumbernumber)can be made from the letters S, P, Y, and twodigits from the set of (0, 1, 2,..., 9) without repetition?
#16. A pair of dice are rolled and the sum on their upturned faces is recorded. What is the probability that the sum showing is 8, given that one die is showing a 5?
#20. A box contains two black balls and three gold balls. Two balls are randomly drawn in succession fro the box. a.) If there is no replacement, what is the probability that both balls are black? b) If there is replacement before the second draw, what is the probability that both balls are blacks?
#26. Jack is taking a fouritem truefalse test. He has no knowledge about the subject of the test and decides to flip a coin to answer the items. What is the probability that he receives a perfect score? What is the probability on a 10item test?
Please help me.

We do not do your work for you. Once you have answered your questions, we will be happy to give you feedback on your work. Although it might require more time and effort, you will learn more if you do your own work. Isn't that why you go to school?
However, I will give you a start.
20. With replacement P = # in category/total. Without replacement, category and total are reduced by one each time. Probability of two more events all occurring is found by multiplying the probability of the individual events. 
15X1