Stephanie has a 88% average after 4 tests. What must Stephanie score on the fifth test to have a 90% average? Explain your method
Using my way i got 18
I know im wrong.
Can u help me plzzzzz!
2007-02-04 15:20:58 · 9 answers · asked by CARLOS7DIGITAL 1 in Education & Reference ➔ Homework Help
Average after 4 testsis 88%
Therefore total marks obtained in 4 tests=88*4=352
Average should be 90% aftr the fifth test.
The total should be 90*5=450
Marks to be scored in 5th test
=450-352=98
2007-02-04 15:27:44 · answer #1 · answered by alpha 7 · 0⤊ 0⤋
Stephanie had 4 test with an 88% avg. What is her total points? How many total points will she need to reach a 90%?
Here is how to solve:
1. ((4 * 88) + t) / 5 = 90 where " t " is the next test & 5 is the number of tests taken
2. ((4 * 88) + t) *5 / 5 = 90 * 5 multiply out the 5
3. ( 4 * 88) + t = 450
4. 352 + t = 450 Solve for " t "
5. t = 98
6. ((4 * 88) + 98) / 5 = Avg. Plug answer into equation #1
7. 450 / 5 = avg.
8. 90 = avg.
She will need a 98% on her test to bring her average up to 90%
2007-02-04 23:53:10 · answer #2 · answered by Anonymous · 0⤊ 0⤋
No matter what she got on each of the earlier tests, we know that the four tests add up to 352, because to get an 88% average over 4 tests, you take [test total] / 4 = 88... Here, that numerator must be 352.
If that's the case, then we know, including the fifth test, [test total] / 5 = 90.
Multiply both sides by 5, you get [test total] = 90 * 5 = 450
Subtract out the 352 from the first four tests, and you get 98. So she has to get a 98 on this last test to get a total of 450 from all five tests.
DIFFERENT METHOD:
If she got an 88% four times, that means she was 2% below 90% four times... 2% * 4 = 8%... So now she must get a score that's 8% above 90% for it to even out... in other words, she must get a 98%
2007-02-04 23:26:42 · answer #3 · answered by ufralphie 2 · 0⤊ 0⤋
Since her average was 88% we can pretend she got exactly that on all four tests.
So that leaves us with the following equation:
(88 + 88 + 88 + 88 + X)/5 = 90 (that's the four known scores, plus the mystery score, divided by the number of tests)
(352 + X)/5 = 90
352 + X = 450
X = 450 - 352
X = 98
Check:
88 + 88 + 88 + 88 + 98 = 450
450/5 = 90
voila, hope this helps
2007-02-04 23:34:08 · answer #4 · answered by LX V 6 · 0⤊ 0⤋
Saying the five tests were worth 100 points each, there are 500 points total. 450 points are needed to acieve a 90%. We can say that if her average is an 88, then she could have gotten an 88 on every test, it doesnt matter. so 88x4=352. This means she needs 98 points to get to 450 and acieve a 90%.
2007-02-04 23:57:46 · answer #5 · answered by mattdevivo 2 · 0⤊ 0⤋
I got she got to get a 100 on the next test to have an 90% average. this is what I did:
88+88+88+88+100= 452
452/5=90
Got it!
2007-02-04 23:30:15 · answer #6 · answered by sexychoche25 1 · 0⤊ 2⤋
88 X .8 ( represents 4/5 of the test)
=70.4
take 90-70.4 ( u want 90 altogether and 70.4 is what u got with the other tests, so (90-70.4=19.6) thats what u need on ur last test, out of 1/5 of 5
so 1/5 of 5 is 20
u need 19.6/20 on the fifth test, or 98%
2007-02-04 23:26:25 · answer #7 · answered by Loki 1 · 0⤊ 0⤋
use addition...duh!...2% .......88% + 2%=90%
or 90% - 88% = 2%...well at least that what i was taught
2007-02-04 23:26:18 · answer #8 · answered by Anonymous · 0⤊ 2⤋
Uh... that's math...
2007-02-04 23:26:17 · answer #9 · answered by ... 3 · 0⤊ 0⤋