The mean of four numbers is 71.5. If three of the numbers are 58, 76, and 88, what is the value of the fourth number?

eddy2017

eddy2017

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Hi,

The mean of four numbers is 71.5. If three of the numbers are 58, 76, and 88, what is the value of the fourth number?
a. 64
b. 60
c. 76
d. 82

I knw the mean or average(arithmetic mean) is calculated by adding all the terms in the data set given.
here the addition has already been done
58, 76, and 88 =222
I add up the three numbers given and tried adding each number in the answer choice and divide the result by 4 but I have gotten no 51.7
what am I doing wrong here?.

tried 222+58 =280/4 =70
tried 222=60 =282/4 =70.5 no
222 + 76=288/4 =74.5 no

thanks,
eddy
 
If you know the mean of those 4 numbers can you figure out their sum?
 
blamocur said:
If you know the mean of those 4 numbers can you figure out their sum?
Click to expand...
I was used to add all the terms up and divide them by the amount of numbers in the data set. this is a bit off the beaten path for me. the way i reasoned it above is all that comes to mind right now
 
I am thinking of something now. I have learned here that variables are for unknown quantities or factors. wait let set something up and see if you like it.
 
eddy2017 said:
Hi,

The mean of four numbers is 71.5. If three of the numbers are 58, 76, and 88, what is the value of the fourth number?
a. 64
b. 60
c. 76
d. 82

I knw the mean or average(arithmetic mean) is calculated by adding all the terms in the data set given.
here the addition has already been done
58, 76, and 88 =222
I add up the three numbers given and tried adding each number in the answer choice and divide the result by 4 but I have gotten no 51.7
what am I doing wrong here?.

tried 222+58 =280/4 =70
tried 222=60 =282/4 =70.5 no
222 + 76=288/4 =74.5 no

thanks,
eddy
Click to expand...
Your process is correct but I think you are making silly arithmatic mistakes.
eddy2017 said:
The mean of four numbers is 71.5
Click to expand...

Then you say:

eddy2017 said:
I have gotten no 51.7
Click to expand...

Why should you???
 
58
Subhotosh Khan said:
Your process is correct but I think you are making silly arithmatic mistakes.


Then you say:



Why should you???
Click to expand...
I tried them all but got no 71.5. let me recheck and I'll get back to you. thank you for the headsup
 
eddy2017 said:
I was used to add all the terms up and divide them by the amount of numbers in the data set. this is a bit off the beaten path for me. the way i reasoned it above is all that comes to mind right now
Click to expand...
The mean is the sum divided by 4. What number has to be divided by 4 to get 71.5 ?
 
Oh, lol ,what a math fool, lol
the first one did it
i was inputting the wrong info
222+ 64 =286/4 =71.5
 
thank you!!!!.
I was going to set up an equation. i have grown so fond of variables here, lol.
58 + 76 + 88 + n /4 = 71.5

I think this one would have done the trick too.
 
eddy2017 said:
Hi,

The mean of four numbers is 71.5. If three of the numbers are 58, 76, and 88, what is the value of the fourth number?
a. 64
b. 60
c. 76
d. 82

I knw the mean or average(arithmetic mean) is calculated by adding all the terms in the data set given.
here the addition has already been done
58, 76, and 88 =222
Click to expand...

You were so close.

What you actually knew was

[math]\dfrac{x + 58 + 76+ 88}{4} = 71.5[/math]
Solve for x.
 
eddy2017 said:
Hi,

The mean of four numbers is 71.5. If three of the numbers are 58, 76, and 88, what is the value of the fourth number?
a. 64
b. 60
c. 76
d. 82

I knw the mean or average(arithmetic mean) is calculated by adding all the terms in the data set given.
here the addition has already been done
58, 76, and 88 =222
I add up the three numbers given and tried adding each number in the answer choice and divide the result by 4 but I have gotten no 51.7
what am I doing wrong here?.

tried 222+58 =280/4 =70
tried 222=60 =282/4 =70.5 no
222 + 76=288/4 =74.5 no

thanks,
eddy
Click to expand...
Why didn't you try 64?
 
at post 5 i made a mistake. instead of trying 64 the first number in the choice i inadvertently tried 58
 
eddy2017 said:
do I have to put parentheses around the 4 too?. hesitant there.
Click to expand...
No, 4 is fine without parentheses. You need parentheses around the some because otherwise it would mean "58 + 76 + 88 + (n / 4) = 71.5" since division has higher precedence than addition.
 
eddy2017 said:
I like this better. less complicated
Click to expand...
The whole practical point of algebra is to reduce the burden on your imagination.

Had you said to yourself

What do I need to do?

Find a number. OK, name it.

To find a single number, I need one equation.

What is it?
 
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