# Spinner - using probabilities

• Oct 1st 2012, 11:25 AM
jthomp18
Spinner - using probabilities
Consider a fair spinner with five sections labeled 1, 2, 3, 4, and 5. The probability for landing on region 1 is one-fifth, region 2 is one-eighth, region 3 is one-third, and regions 4 and 5 have unknown probabilities. The spinner can only land on one section at a time.

Describe the possible probabilities of landing in region 4 or region 5. Draw a diagram to assist your explanation.

Can someone help me figure out how to complete this problem?
• Oct 1st 2012, 01:28 PM
Plato
Re: Spinner - using probabilities
Quote:

Originally Posted by jthomp18
Consider a fair spinner with five sections labeled 1, 2, 3, 4, and 5. The probability for landing on region 1 is one-fifth, region 2 is one-eighth, region 3 is one-third, and regions 4 and 5 have unknown probabilities. The spinner can only land on one section at a time.
Describe the possible probabilities of landing in region 4 or region 5. Draw a diagram to assist your explanation.

The sum of all the probabilities must equal one.
If $p_4~\&~p_5$ are the missing the what must $p_4+p_5=~?$
• Oct 2nd 2012, 04:45 AM
jthomp18
Re: Spinner - using probabilities
P4= 1/5 and P5=1/7

Would this be correct? I can draw the graph using the sections. What do I do for "Describe the possible probabilities of landing in region 4 or region 5?"
• Oct 2nd 2012, 05:44 AM
Plato
Re: Spinner - using probabilities
Quote:

Originally Posted by jthomp18
P4= 1/5 and P5=1/7
Would this be correct? I can draw the graph using the sections. What do I do for "Describe the possible probabilities of landing in region 4 or region 5?"

Do the probabilities add up to 1. NO, they add 1.001.
It must be $p_4+p_5=\frac{42}{120}~?$ WHY?
• Oct 2nd 2012, 12:42 PM
jthomp18
Re: Spinner - using probabilities
Okay so apparently my way is incorrect of finding p4 and p5. HOW do I determine what p4 and p5 are? I will have to create a pie chart showing all 5 of my regions .. so I would think my denominator would be a whole number (2,3,4,etc) .. I am confused on the 42/120?
• Oct 2nd 2012, 01:14 PM
Plato
Re: Spinner - using probabilities
Quote:

Originally Posted by jthomp18
Okay so apparently my way is incorrect of finding p4 and p5. HOW do I determine what p4 and p5 are? I will have to create a pie chart showing all 5 of my regions .. so I would think my denominator would be a whole number (2,3,4,etc) .. I am confused on the 42/120?

$1=p_1+p_2+p_3+p_4+p_5=\frac{1}{5}+\frac{1}{8}+ \frac{1}{3}+p_4+p_5$ so what is $p_4+p_5=~?$

Now there is absolutely no way to know exactly the values $p_4~\&~p_5~.$
• Oct 2nd 2012, 01:17 PM
jthomp18
Re: Spinner - using probabilities
Okay, I will just have to ask my instructor for further detail. If there is no way to know exactly what p4 and p5 are then why does my question ask to find the probabilities of it landing on p4 and p5. So apparently the question cannot be answered if there is not a way for all 5 parts to equal 1.
• Oct 2nd 2012, 01:32 PM
Plato
Re: Spinner - using probabilities
Quote:

Originally Posted by jthomp18
why does my question ask to find the probabilities of it landing on p4 and p5. So apparently the question cannot be answered if there is not a way for all 5 parts to equal 1.

Quote:

Originally Posted by jthomp18
Consider a fair spinner with five sections labeled 1, 2, 3, 4, and 5. The probability for landing on region 1 is one-fifth, region 2 is one-eighth, region 3 is one-third, and regions 4 and 5 have unknown probabilities. The spinner can only land on one section at a time.
Describe the possible probabilities of landing in region 4 or region 5. Draw a diagram to assist your explanation.

That question ask for exact values.
It says "Describe the possible probabilities of landing in region 4 or region 5."