# probability word problem help, please....

• Jan 8th 2009, 11:23 AM
JoanneMac
Ok, I have 3 word problems dealing with probability that I need help with. So here they are:(Wondering)

1.Suppose a contest offers \$1,000 to the person who can guess the winning 4 digit number. How many possibilities are there?

2. Two marbles are drawn froma bag containing 6 white, 4 red, and 6 green marbles. Find the probability of both marbles being white.

3. Suppose there are 10 items on a true-false test. The person taking the test does not read the questions; he just answers each question randomly. What is the probability of his guessing all answers correctly?

Thanks in advance for any help!
• Jan 8th 2009, 11:35 AM
number 2
Well number 2 is relatively easy you take the amount of white marbles 6 then put it over the total amount of marbles i.e 6+4+6 so u get 6/16(for the prob. that the first marble is white) then multiply that by 5/15(i.e. prob that second marble is white) then u get 17/24 for
Quote:

Originally Posted by JoanneMac
Ok, I have 3 word problems dealing with probability that I need help with. So here they are:(Wondering)

1.Suppose a contest offers \$1,000 to the person who can guess the winning 4 digit number. How many possibilities are there?

2. Two marbles are drawn froma bag containing 6 white, 4 red, and 6 green marbles. Find the probability of both marbles being white.

3. Suppose there are 10 items on a true-false test. The person taking the test does not read the questions; he just answers each question randomly. What is the probability of his guessing all answers correctly?

Thanks in advance for any help!

• Jan 8th 2009, 11:40 AM
Number three i believe that u multiply his chances of getting each question correct i.e he has 1/2 chance of getting number one corect then 1/2 chance of getting number two correct so u end up with 1/2x by itself 10 times or 1/2^10 and u get an answer of 1/1024
Quote:

Originally Posted by JoanneMac
Ok, I have 3 word problems dealing with probability that I need help with. So here they are:(Wondering)

1.Suppose a contest offers \$1,000 to the person who can guess the winning 4 digit number. How many possibilities are there?

2. Two marbles are drawn froma bag containing 6 white, 4 red, and 6 green marbles. Find the probability of both marbles being white.

3. Suppose there are 10 items on a true-false test. The person taking the test does not read the questions; he just answers each question randomly. What is the probability of his guessing all answers correctly?

Thanks in advance for any help!

• Jan 8th 2009, 11:42 AM
i think number one is just that the amount of possibilities are 9999
• Jan 8th 2009, 12:24 PM
mr fantastic
Quote:

i think number one is just that the amount of possibilities are 9999

You mean(9)(9)(9)(9) = 9^4, right ....?
• Jan 8th 2009, 12:26 PM
mr fantastic
Quote:

Originally Posted by JoanneMac
[snip]

2. Two marbles are drawn froma bag containing 6 white, 4 red, and 6 green marbles. Find the probability of both marbles being white.

[snip]

Drawing a tree diagram is always a good idea for these sorts of questions.
• Jan 8th 2009, 12:43 PM
TheMasterMind
Quote:

Originally Posted by JoanneMac
Ok, I have 3 word problems dealing with probability that I need help with. So here they are:(Wondering)

1.Suppose a contest offers \$1,000 to the person who can guess the winning 4 digit number. How many possibilities are there?

2. Two marbles are drawn froma bag containing 6 white, 4 red, and 6 green marbles. Find the probability of both marbles being white.

3. Suppose there are 10 items on a true-false test. The person taking the test does not read the questions; he just answers each question randomly. What is the probability of his guessing all answers correctly?

Thanks in advance for any help!

3. The chance of getting any one question right is 50%, or 0.5.

The chance of getting all 10 right is (0.5)^10, or .0009765625. If we round this to .001, that means you have about one chance in a thousand of getting them all right, or 0.1%
• Jan 8th 2009, 05:54 PM
mr fantastic
Quote:

Originally Posted by TheMasterMind
3. The chance of getting any one question right is 50%, or 0.5.

The chance of getting all 10 right is (0.5)^10, or .0009765625. If we round this to .001, that means you have about one chance in a thousand of getting them all right, or 0.1%

*Ahem* .... Which confirms reply #3 .....