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avatar+1715 

If we toss a pair of dice, what is the probability that a sum of 7 will appear?

 

A./ 7/36


B. 1/6


C. 1/2


D. 1/36

 


Four coins are tossed at the same time. What is the probability that exactly 3 heads will appear?

 

A. 1/2


B. 1/4


C. 1/16


D. 1/8

 May 8, 2020
 #1
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+1

36 possible rolls  

6 1

5 2

4 3    are all 7's   and two ways of rolling each of the,      6/36 = 1/6

 May 8, 2020
 #2
avatar+1543 
+4

So basically we first need to figure out how much pairs that add to 7.

 

1,6

6,1

2,5

5,2

3,4

4,3

 

There are 6*6 = 36 possible outcomes,  so 6/36 = 1/6

 

See guest's post below for 2).

 

If you don't understand anything feel free to ask.

 May 8, 2020
edited by hugomimihu  May 8, 2020
 #3
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+1

Hmmmm       16 possibilities for the coin toss

 

there are 4 possibles for EXACTLY 3 heads

HHHT

HHTH

HTHH

THHH       4 OUT OF 16 =   1/4

 May 8, 2020
 #4
avatar+1543 
+3

Intresting point.

 

There are 4 ways of only 1 heads,

 

HTTT

THTT

TTHT
TTTH

 

2heads,

 

HHTT

HTHT
HTTH

THHT

THTH

TTHH
 

3 heads

 

HHHT
HHTH
HTHH
THHH

 

4 heads
 

HHHH

 

0 heads

 

TTTT

 

Good point it's 4/16


I'll revise my answer thanks for the correction!

hugomimihu  May 8, 2020
edited by hugomimihu  May 8, 2020
 #5
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0

The probability is =4! / [3!.1!.2^4] =24 /[6 x 16] = 1/4

Guest May 8, 2020

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