# Math Is Fun Forum

Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

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## #1 2024-05-15 13:21:08

mathxyz
Member
From: Brooklyn, NY
Registered: 2024-02-24
Posts: 1,053

### Three Probability Problems

A coin is flipped 5 times. What is the probability of landing on heads 3 out of 5 times?

The probability of rain for the next 3 days is 60 percent. What is the probability of no rain for 2 out of 3 days?

A book has 300 pages. What is the probability of opening and closing the book 4 consecutive times and landing on any page between 100 and 250?

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## #2 2024-05-15 17:36:44

Keep_Relentless
Member
From: Queensland, Australia
Registered: 2024-05-05
Posts: 61

### Re: Three Probability Problems

I notice your questions have gotten trickier.

I'll make a start on the first one.

It's useful to consider the number of different ways you could have three heads.
You could have:

HHHTT
HHTHT
HHTTH

HTHHT
HTHTH
HTTHH

THHHT
THHTH
THTHH

TTHHH

That's 10 possibilities... out of how many in total?

K_R

"The most incomprehensible thing about the world is that it is comprehensible." -Albert Einstein.

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## #3 2024-05-16 01:29:05

mathxyz
Member
From: Brooklyn, NY
Registered: 2024-02-24
Posts: 1,053

### Re: Three Probability Problems

Keep_Relentless wrote:

I notice your questions have gotten trickier.

I'll make a start on the first one.

It's useful to consider the number of different ways you could have three heads.
You could have:

HHHTT
HHTHT
HHTTH

HTHHT
HTHTH
HTTHH

THHHT
THHTH
THTHH

TTHHH

That's 10 possibilities... out of how many in total?

K_R

Not my questions at all. Questions come from different online sites.

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