probability Qs plz help!! (1 Viewer)

[rego2]

hi im having trouble working out these question could someone please explain it to me?

1)How many 3 digit numbers can be made from the digits 2,3,5,8, and 9 using each digit only once?

2)How many 4-digit odd numbers can be made using the digits 2,5,8 and 9?


3)Todd is playing a computer game. In a game he has to choose different paths to follow. He has to choose between 3 different paths at 4 stages. How many different paths can he choose?

 

[rego2]

ah thank you so much
btw i love you art work lol

 

[rego2]

i think ur wrong on question 3... the answer in my book is 36..

 

[haboozin]

because he wrote 4 paths instead of 3...


theres 3 paths but 4 stages

 

[rego2]

3)Todd is playing a computer game. In a game he has to choose different paths to follow. He has to choose between 3 different paths at 4 stages. How many different paths can he choose?

yeh for the answer in my text book it said 36.. this is so confussing me..
could some1 help?

 

[PC]

1. Number of possible numbers = 5 x 4 x 3 = 60

2. Number of possible numbers = 4 x 4 x 4 x 2 = 128
You have to put either 5 or 9 as the last digit to make it odd, then you can use any one of the four digits available in each of the other places. Well ... the question doesn't say you can't.

3. Number of paths = 3 x 3 x 3 x 3 = 81
There are three choices at each stage and there are four stages.
Just like tossing a coin four times, except at each toss there are only two results, so number of outcomes = 2 x 2 x 2 x 2 = 16.

Hope this helps. Anti's tree diagram is spot on.

 

[rego2]

1. Number of possible numbers = 5 x 4 x 3 = 60

2. Number of possible numbers = 4 x 4 x 4 x 2 = 128
You have to put either 5 or 9 as the last digit to make it odd, then you can use any one of the four digits available in each of the other places. Well ... the question doesn't say you can't.

3. Number of paths = 3 x 3 x 3 x 3 = 81
There are three choices at each stage and there are four stages.
Just like tossing a coin four times, except at each toss there are only two results, so number of outcomes = 2 x 2 x 2 x 2 = 16.

Hope this helps. Anti's tree diagram is spot on.

Wow great help Pc thanks alot

But for question 1) how did u get 5 x 4 x 3?

and i also had another question.

The arrow is spun and will point to one of the four colours when it stops.
If the arrow is spun stwice, what is the probability that it points to the same colour both tims it stops?
The answer is 1/4 but why cant i do it as 1/4 x 1/4 = 1/16?

 

[ephemeral]

because the second spin is independent from the first. The initial colour you get is irrelevant. I think 1/16 would be the answer if they specified the colour on which it had to land twice.

Question 1 is simply 5*4*3 because you can use 5 letters for the first, 4 for the second (you can only use each once) and 3 for the third. So you have 5 letters to choose from, then 4, then 3.

 

[PC]

because the second spin is independent from the first. The initial colour you get is irrelevant. I think 1/16 would be the answer if they specified the colour on which it had to land twice.

That question caught a lot of people out that year. The Board of Studies put out a CD summarising all the responses to that particular exam paper. It appeared that most people picked 1/16 rather than 1/4.

I think what tricked people was that the arrow in the diagram was pointing to red, so people must have thought that the question was asking about getting two reds in a row.