Probability

[lacoste]

Qst A).

A coin is tossed 3 times and you note that the coin lands heads exactly twice. What is the probability that the first toss was the tail?

Help please, any help appreciated

[Flaming_Arrow]

whats the answer?

[lacoste]

whats the answer?

Qst. A)
1/3

[lacoste]

These questions are from Conditional and Multiplication Rule Probability.. Including Qst. A)
Im not sure how they got the answers.

Qst B) A pair of fair dice are rolled. Find the probability that both numbers are odd given that the first die shows a number less than 4?

[Mao]

A) I won't use maths, because the question is not too complicated:

exactly two H, meaning the possible combinations are: THH, HTH, HHT

hence the chance of T first is 1/3

B)

both odd = first odd * second odd



second odd is 1/2

hence both odd given that first is less than 4 would be 1/3

[Flaming_Arrow]

1.


 

[lacoste]

1.


 

Why is it 3C2?
Does that mean 3 Combination? / a coin is tossed 3 times.

Shouldn't it be 3(0.5 * 0.5), because its 2 heads(50/50 chance) and three tosses?

[Flaming_Arrow]

1.


 

Why is it 3C2?
Does that mean 3 Combination? / a coin is tossed 3 times.

Shouldn't it be 3(0.5 * 0.5), because its 2 heads(50/50 chance) and three tosses?

3C2 as in 2 heads in 3 tosses

[lacoste]

what does that equate to?

so 3C2 is equal to just 3?

why havnt i heard of"3C2" notation is that part of permuations or sumthin

[Flaming_Arrow]

its nCr