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# Average Mark

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Dorris's average mark out of 3 tests was 82.

Her last mark was 3/2 times her first mark. The middle mark was 86.

What was the difference between her 1st and last mark?

Guest Apr 23, 2017

#4
+5552
+3

Let's call the first test score a, second test score b, and third test score c.

(a + b + c) / 3 = 82

c = 3/2 * a = 3a/2

b = 86

Substitute the values we know for b and c into the first equation.

(a86 + 3a/2) / 3 = 82

Solve for a.

a + 86 + 3a/2 = 82 * 3

a + 3a/2 = 246 - 86

2a/2 + 3a/2 = 160

5a/2 = 160

a = 160 * 2/5 = 64

Substitute the value we found for a into the second equation to find c.

c = 3(64)/2 = 96

a - c = 64 - 96 = -32

...so her score improved 32 points from her first test to her last test!

hectictar  Apr 23, 2017
Sort:

#1
+1

f+3/2f+86=3(82)=246

5/2f=160

f=64

l=96

diff=32

Guest Apr 23, 2017
#2
0

Care to explain what's going on?

Guest Apr 23, 2017
#5
0

If yall kept it simpler it would be simpler and SAT/GRE would be kaboom

but ok

Let f: first score

Q states that: f+3/2f+86=3 times average=3(82)=246

5/2f=246-86

5f=320

f=64

Let l: last score

l=3/2f=64.(3/2)=96

diff=96-64=32

if yall need to slow it down to really pedantic slowness go widda next answ

Guest Apr 23, 2017
#3
0

Did you look under your first post?!

Guest Apr 23, 2017
#4
+5552
+3

Let's call the first test score a, second test score b, and third test score c.

(a + b + c) / 3 = 82

c = 3/2 * a = 3a/2

b = 86

Substitute the values we know for b and c into the first equation.

(a86 + 3a/2) / 3 = 82

Solve for a.

a + 86 + 3a/2 = 82 * 3

a + 3a/2 = 246 - 86

2a/2 + 3a/2 = 160

5a/2 = 160

a = 160 * 2/5 = 64

Substitute the value we found for a into the second equation to find c.

c = 3(64)/2 = 96

a - c = 64 - 96 = -32

...so her score improved 32 points from her first test to her last test!

hectictar  Apr 23, 2017
#6
+79819
0

Calm down ,guest......we appreciate your answer, but there may be several ways to solve the same thing......just because you think that your answer is superior may not make it so.....

Hectictar's answer isn't any more "pedantic" than any other one........

CPhill  Apr 23, 2017
#7
0

Please dont be preposterously presumptuous: you really do not know what's in my mind. It's very offensive indeed when you contend vigorously that I believe my answer is better (I totally don't) and when you then decide to tell me to calm down. H's answer is completely fine. I will help out elsewhere where how we did things 55 years ago (i.e. very quickly, in our heads, with the correct answer, cross-checked and assuredly) isn't deprecated. Bye, Felicia.

Guest Apr 23, 2017
#8
+5552
0

Bye Felicia??? 😂😂

No Guest! Don't leave!

You aright after all..

hectictar  Apr 23, 2017
#9
+833
0

Please dont be preposterously presumptuous: you really do not know what's in my mind. It's very offensive indeed when you contend vigorously that I believe my answer is better …

Oh, my . . . This is great! We need another old gasbag! A companion for the forum’s Banker –one who articulates more, but is even less intelligible.

This one couches his precipitated blarney in unintelligible, self-absorbed self-important egotisms, presented in glorious century-old syntax, with missing apostrophes, commas, and periods, as a true testament to his “cross-checking” skills). He's hip, though, he ends his archaic writing with a modern meme: “Bye, Felicia.” (A farewell to someone considered insignificant.)

Like the banker, he is not a “has been,” rather he’s a “never were” member in a group of wannabes – mathematicians, probably. He’s practiced indignant criticism all of his life because it’s the only way he can create a contrast to measure his milestones of achievement.

I hope he stays around. We stylish, superior trolls really relish rare, refined dinning of preposterously presumptuous pretentious phrases in our smorgasbord.  We also like to listen to the villains in the old Scooby-do cartoons while we enjoy our meal.

GingerAle  Apr 24, 2017
edited by GingerAle  Apr 24, 2017

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