please help! I have a problem on my math homework and i'm not sure whether I should add multiply, etc. also can someone please explain when to add and when to multiply? 10 cards are numbered 1 through 10. the cards are well shuffled and drawn at random. if two cards are drawn with replacement, find the probability of choosing a prime number in both the first and second draw. Thanks!
A basic definition of probability is: # desired / # possible Now, there are 2, 3, 5, 7 as prime numbers, or 4 of them. the probability of getting a prime number is 4/10 or 2/5. Now, think of a coin flip. flip it twice, what is the probability of two tails. well, the possibilities are: TT, TH, HT, HH or 4 of them. ONE is what you want, so, the probability must be 1/4. The probability of ONE tails in the first toss is 1/2; and on the second is 1/2. How are you gonna get 1/4 from two 1/2. clearly, 1/2 x 1/2 In your case, you have the same problem. it is 2/5 x 2/5. It is important that you specify if it is with replacement or without replacement. A totally different procedure is used without replacement, since the probability changes each time you pull a card. always, tony
A total of 10 cards. 4 of them are prime chance of getting a primer is 4/10 then you place this card back and draw another card. Chance of getting a prime on the second draw is 4/10 so the chance of getting primer followed by another prime is (4/10)*(4/10) = 16/100=4/25 dnadan1
Ok so the prime numbers 1-10 are 2,3,5,7 so that's 4/10 then double 4+4 so I believe for sure it's 8/10 which reduces to 4/5.