MATH 157
posted by Rayna .
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
Respond to this Question
Similar Questions

Math
A license plate is to consist of two letters followed by three digits. How many different license plates are possible if the first letter must be a vowel, and repetition of letters is not permitted, but repetition of digits is permitted? 
Math
Did I do this problem right? How many three symbol codes (letternumbernumber) can be made from the letters S,P,Y and two digits from the set {0,1,2,...,9} without repetition? 
MATH Prob.
How many threesymbol codes can be formed from the letters I, S, P, and Y without repetition? 
math 157
How many threesymbol codes (letter, letter, number) can be made from the letters S, P, Y and one digit fro the set {0, 1, 2,...9} without repitition? 
math157
How many threesymbol codes (letternumbernumber) can be made from the letters S, P, Y and two digits from the set {0, 1, 2, …,9} without repetition? 
Mat 157
How many threesymbol codes (letterletternumber) can be made from the letters, S,P,Y, and one digit from the set {0,1,2,...,9] without repetition? 
math
How many threesymbol codes can be formed from the letters I,S,P, and Y without repetition? 
Math
1.) A security code has seven characters. Each code begins with two digits, then two letters, and finally three digits. the number of distinct security codes possible if repetition is allowed? 
math30
A security code used to consist of two odd digits, followed by four even digits. To allow more codes to be generated, a new system uses two even digits, followed by any three digits. If repeated digits are allowed, the increase in … 
Math
how many three letter security codes can be made from 4 letters A,B,C,D without using a letter twice?