Question 1006157: I cannot seem to find how to resolve this question.
I made average pies, tried adding equations. I do not know what to do next! Thanks for your help.
The average between a and b is 9, between b and c is 6, between c and d is 15. What is the average between d and a?
Thank you so very much!
Caroline
Found 3 solutions by josmiceli, Theo, MathTherapy:
Answer by josmiceli(19441)   (Show Source):
Answer by Theo(13342)  (Show Source):
You can put this solution on YOUR website! (a + b)/2 = 9
(b + c)/2 = 6
(C + D)/2 = 15
from this you get:
a + b = 18
b + c = 12
c + d = 30
solve for b in a + b = 18 to get b = 18 - a
solve for c in b + c = 12 to get c = 12 - b
start with c + d = 30
replace c with 12 - b to get:
12 - b + d = 30
replace b with 18 - a to get:
12 - (18 - a) + d = 30
simplify to get:
12 - 18 + a + d = 30
combine like terms to get -6 + a + d = 30
add 6 to both sides of this equation to get:
a + d = 36
divide both sides of this equation by 2 and you get:
(a + d)/2 = 18
the average of a + d is equal to 18.
i believe that's the answer you are looking for.
Answer by MathTherapy(10555)  (Show Source):
You can put this solution on YOUR website!
I cannot seem to find how to resolve this question.
I made average pies, tried adding equations. I do not know what to do next! Thanks for your help.
The average between a and b is 9, between b and c is 6, between c and d is 15. What is the average between d and a?
Thank you so very much!
Caroline
If 9 is the average of a and b, then sum of a and b is 2(9), or 18, so a + b = 18______b = 18 - a ------- eq (i)
If 6 is the average of b and c, then sum of b and c is 2(6), or 12, so b + c = 12 -------- eq (ii)
If 15 is the average of c and d, then sum of c and d is 2(15), or 30, so c + d = 30 ------ eq (iii)
18 – a + c = 12 ------- Substituting 18 – a for b in eq (ii)
c = a – 18 + 12
c = a – 6 -------- eq (iv)
a – 6 + d = 30 ------- Substituting a - 6 for c in eq (iii)
a + d = 30 + 6
a + d = 36
Average of a + d:  , or  , or 
|
|
|
