Math destroyer test 9 # 11

[aliss4]

A penny, a nickel, and a quarter are tossed in the air. What is the probability that nickel and the penny will both come up heads?

Shouldn't be 1/2 instead of 1/4?

HHT HTH THH HHH
4 X1/8 = 1/2

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[SLOBrule]

A penny, a nickel, and a quarter are tossed in the air. What is the probability that nickel and the penny will both come up heads?

Shouldn't be 1/2 instead of 1/4?

HHT HTH THH HHH
4 X1/8 = 1/2

Since you are asked the probability of two coins coming up heads, it is just

1/2 x 1/2 = 1/4
HT HT HH

 

[AlbinoPolarBear]

A penny, a nickel, and a quarter are tossed in the air. What is the probability that nickel and the penny will both come up heads?

Shouldn't be 1/2 instead of 1/4?

HHT HTH THH HHH
4 X1/8 = 1/2

P(penny head) = 1/2
P(nickel head) = 1/2

P(penny head)*P(nickel head) = 1/2 * 1/2 = 1/4

Or if you want to do the tree (PNQ):
HHH*
HHT*
HTH
HTT
THH
THT
TTH
TTT

= 2/8 = 1/4

 

[toothhornet88]

A penny, a nickel, and a quarter are tossed in the air. What is the probability that nickel and the penny will both come up heads?

Shouldn't be 1/2 instead of 1/4?

HHT HTH THH HHH
4 X1/8 = 1/2

With this question you don't even look at the quarter. Its just there to throw you off. Just focus on what they are asking you (nickel and penny)

prob of tossing a head for a penny and nickel are 1/2 each, so 1/2*1/2= 1/4

 

[aliss4]

Since you are asked the probability of two coins coming up heads, it is just

1/2 x 1/2 = 1/4
HT HT HH

I know but we tossed all together. So we can't just ignore the third one. Then, what's the difference between tossing two coins or three coins together?

 

[aliss4]

P(penny head) = 1/2
P(nickel head) = 1/2

P(penny head)*P(nickel head) = 1/2 * 1/2 = 1/4

Or if you want to do the tree (PNQ):
HHH*
HHT*
HTH
HTT
THH
THT
TTH
TTT

= 2/8 = 1/4

so basically we are not allowed to have more than two heads right?

 

[aliss4]

so basically we are not allowed to have more than two heads right?

Oh never mind. Got it. thanks

 

[SLOBrule]

I know but we tossed all together. So we can't just ignore the third one. Then, what's the difference between tossing two coins or three coins together?

The 3rd coin has nothing to do with the outcome of the other two coins being asked about. It is probably placed in the question as a distraction, it should be ignored in this case.