How to find the average!?!?!?

Question

Each student listed has taken 3 math tests. Find the score each student needs on the next test in order to have an 80 average!!?!?!
(test 1 then 2 then 3 then the line is where the answer goes)
Bill-78,78,78 _____
Jill-68,79,74 _____
Phil-72,82,82 _____
Will-91,64,76______

PLEASE HELP! i don't get it!

Answer 1

4 tests require a total of 320 to give 80% average.

Required scores for Test 4 shown below:-

Pupil_Test 1_Test 2_Test 3_Test 4___Total
Bill____78____78____78____86_____320
Jill____69____79____74____98_____320
Phil___72____82____82____84_____320
Will___91____64____76____89_____320

Answer 2

Okay, so you need to set up an inequality.

(78 + 78 + 78 + x) / 4 >= 80

(234 + x) / 4 >= 80

234 + x >= 320

x >= 86

So he needs at least an 86 to get an 80 average. Follow suit for the rest of em.

Answer 3

add all of bills scores then divide by 3 b/c there is 3 numbers that bill has. So, 78+78+78=234 then divide by 3. you get your average which is 78.

do that with Jill phil will.
Hope this helps

Answer 4

try this...where "x" is the next test score
(78+78+78+x)/4=80
(234+x)/4=80 Multiply 4 to both sides to cancel the fraction:
234+x=320 Subtract 234 from both sides to get x:
86 is the answer for the first one.
Do the same thing for the rest and you will get your answers.

Answer 5

okay. add the numbers together and divide by how many there were.
Bill= 78+78+78=234. 234/3=78(avg)
Jill= 68+79+74=221. 221/3= 73 2/3(avg)

etc...

Answer 6

(.78*.25) +(.78*.25) + (.78*.25) + (.25x) = .8
repeat for the others
each test is .25 of theyre grade

Answer 7

add bill's scores then divide by 3
add jill's scores then divide by 3
same thing with phill and will

Answer 8

Let first exam score=A, second=B, third=C, fourth=D

80=(A+B+C+D)/4

Answer 9

Lol I do this everyday for my gradese.

U guys help me out:
http://answers.yahoo.com/question/index;_ylt=AuUDHPrHt2Ibf7K8cJwvRynsy6IX;_ylv=3?qid=20071211173843AA0Pv5s

Answer 10

bill-86
jill-99
phil-84
will-89