If the average (arithmetic mean) of a, b, c, and d is equal to the average of a, b, and c, what is d in terms of a, b, and c?

Question

inowalst · Answer

I got: $$\frac{ a+b+c }{ 3 }$$Since for the mean, its to add up all the numbers and divide the sum by the number of numbers.

inowalst · Answer

@TheSmartOne

thesmartone · Answer

Do if we take what your question gave us we get...

$\sf\Huge \frac{a+b+c+d}{4} = \frac{a+b+c}{3}$

thesmartone · Answer

So we cross multiply and we just solve for d @inowalst

inowalst · Answer

Oh okay.

inowalst · Answer

a + b + c. Cancel out?

thesmartone · Answer

we can't really do that. Unless it was $\sf a \times b \times c$

inowalst · Answer

Ohh. :/ Okay.

thesmartone · Answer

$\sf\huge 3(a+b+c+d) = 4(a+b+c)$

inowalst · Answer

I have a question..

thesmartone · Answer

Or we could do it like

$\sf\huge 12 \times(\frac{a+b+c+d}{4}) = 12 \times (\frac{a+b+c}{3})$

thesmartone · Answer

Which ofc gets us back to

$\sf\huge 3(a+b+c+d) = 4(a+b+c)$

inowalst · Answer

Ohh okay. I think I found the answer because I have options and you said one of them.

thesmartone · Answer

Coolio :)

inowalst · Answer

Thank you!

theraggedydoctor · Answer

dot.