On the first 4 tests of this term your average is 84%. If you think you can score 94% on all remaining tests, how many more tests do you need to bring your average up to a 90%
2006-09-06 10:20:52 · 13 answers · asked by many men 1 in Science & Mathematics ➔ Mathematics
Let's see...
84% of 4 tests + 94% of x tests = 90% of (x+4) tests
0.84 * 4 + x * 0.94 = 0.90 * (x+4)
Distribute the right half out...
0.84*4+x*0.94 = 0.90*x + 0.90*4
Subtract 0.90*x and 0.84*4 from both sides...
x*0.04 = 0.06*4 = 0.24
Multiply both sides by 100 to make the numbers nicer...
x*4 = 24
Divide both sides by 4..
x = 6
You need to take 6 tests
2006-09-06 10:22:17 · answer #1 · answered by nondescript 7 · 0⤊ 0⤋
6
2006-09-06 10:25:51 · answer #2 · answered by Anonymous · 0⤊ 0⤋
6 times
2006-09-06 10:24:54 · answer #3 · answered by Anonymous · 1⤊ 0⤋
4
2006-09-06 10:22:55 · answer #4 · answered by Anonymous · 0⤊ 2⤋
if the average is calculated after each test, then you would need to get a 94 on two more tests. the first would bring you to a 89 avg. and the 2nd would give you a 91..... avg...
84+94/2=a a+94/2=b b=91....avg.
good luck!!
2006-09-06 10:28:24 · answer #5 · answered by ....hmmm..... 3 · 0⤊ 0⤋
You need six more tests, assuming you score an exact 94 on each one, to reach a 90 average.
2006-09-06 10:26:09 · answer #6 · answered by Abbey 3 · 0⤊ 0⤋
4 tests, average 84, total points = 4 * 84 = 336
as you take x more tests the number of tests will become 4 + x
the total number of points will increase 336 + 94 (x)
thus the new average = total points/total tests = 90
(336 + 94x) / (4 + x) = 90
336 + 94x = 90x + 360
4x = 24
x = 6
2006-09-06 10:24:07 · answer #7 · answered by Scott S 2 · 1⤊ 0⤋
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2016-12-18 06:03:18 · answer #8 · answered by snelling 4 · 0⤊ 0⤋
6 TIMES.
2006-09-06 10:33:40 · answer #9 · answered by Alana. 3 · 0⤊ 0⤋
good question...6 is the min. to make it...i got a chance to see a couple of answers and the first guy drew it out great for you...not hard at all...im very proud to see there really are some smart people here...most days its.."Can my dog get pregnant from a cat? duhh!
2006-09-06 10:36:46 · answer #10 · answered by Anonymous · 0⤊ 0⤋