A student took 5 papers in an exam, where the total marks were the same for each paper. His marks in these papers were in the proportion of 6:7:8:9:10.
Given that he obtained 5 3 of the total marks, how many papers did he score more than 5 0 % ?
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
well explained
not recommended its a lay man's solution not a mathematican.
Thanks for this
Thanks..
well explained.. :)
Let's assume the maximum marks be 40. Then the marks secured by the student = 120 (3/5 40 5) Adding the above ratios we get 40 (6+7+8+9+10). Now multiply the ratios by a number which will get us to 120. The number will be 3. Thus the ratio becomes 18:21:24:27:30. Just check which of these is above 20 and you have the answer :)
the proportion of the scores is 6:7:8:9:10 if we add up the proportion we get 40 therefore 40a=3/5 and 1/2=(33.33....)a
(33.333....a)/5 =6.66... there are 4 numbers which are larger than 6.66
how explain?//
Assuming that the proportions are real marks, total comes 6+7+8+9+10 is 40....take x as total mark in each subject...so 40/5x=3/5, ,, solving x gives us 13.3... so 50% is around 6.7....m then, 4 subject marks above 6.7 cut off of 50%
6+7+8+9+10=40
40 is three fifths of 66 2/3
Since there are five different tests, each test is out of 13 1/3
Only 6 is less that half of 13 1/3
Let each paper is of y marks so total marks will be of 5y 6:7:8:9:10 is the Proportion. So marks obtained by student in all the 5 papers is equal to =6x+7x+8x+9x+10x =40x Since marks obtained by student in all papers is also 3/5 of 5y Hence 40x=3/5(5y) or x=3y/40 or x=0.075y So mark in paper one =6x=6(0.075y)=0.45y=45% Mark in second paper =7x =0.525y = 52.5% MARK in third paper =8x = 0.6y =60% mark in fourth paper =9x =0.675y=67.5% Mark in fifth paper = 10x =0.75y=75%
Answer: student obtained marks more than 50% in 4 paper.
Let a, b,c,d, e be the total marks the student scored for each paper.
Let k be the common factor for the marks a,b,c,d,e.
a/k:b/k:c/k:d/k:e/k=6:7:8:9:10
Since a,b,c,d,e share a common factor, we can chunk out the single long ratio of five values, to 4 ratios of two values as follow:
a:b=6:7 => 7a=6b,
b:c=7:8 => 8b=7c,
... 9c=8d,
... 10d=9e
Now express a,b,c,d in terms of e:
d=0.9e,
c=0.8e,
b=0.7e,
a=0.6e
Let the total maximum marks for each paper that can be scored be T. Since he obtained 3/5 of the total marks of all the papers:
a+b+c+d+e=3/5 (5T),
4e=3T,
e=0.75T
Hence:
d=0.9e=0.675T,
c=0.8e=0.6T,
b=0.7e=0.525T,
a=0.6e=0.45T
Since the passing ratio is 0.5T (=50%), the student passed 4 papers out of the 5.
Let total marks be 400. Hence score for each paper 400/5 =80. Student has scored (3/5 * 400) 240 marks. His mark in first paper is 6/40 * 240 = 36, which is less than 50% in a paper (50% of 80 = 40). 2nd paper he scores 7/40 * 240=42, which is greater than 40. As we can clearly see that the numerator in the proceeding ratios is only increasing that is 8/40,9/40 and 10/40, all of the 3 scores will naturally be greater than 42(score in second paper which is greater than 50% of the marks in a given exam). Hence answer is 4 papers where he will score more than 50%.
Let A:B:C:D:E= 6:7:8:9:10 Then let the marks in A=k then in B=7k/6 , C=4k/3, D=3k/2, E=5k/3. Hence total marks in addition of marks of {A+B+C+D+E}={ 40k/6} which is equal to 3x/5, where x=total no. of marks. Now 40k/6 = 3x/5 hence k=9x/100. Now since all paper contain equal no. of total marks hence let total marks in each subject be x' then x=5x' hence k=45x'/100. Now put the value of k in the first equation of marks obtained in A,B,C,D,E and we found that leaving A, student scored more than 50% marks in all other subject.. QED
Let total marks be 400. Hence score for each paper 400/5 =80. Student has scored (3/5 * 400) 240 marks. His mark in first paper is 6/40 * 240 = 36, which is less than 50% in a paper (50% of 80 = 40). 2nd paper he scores 7/40 * 240=42, which is greater than 40. As we can clearly see that the numerator in the proceeding ratios is only increasing that is 8/40,9/40 and 10/40, all of the 3 scores will naturally be greater than 42(score in second paper which is greater than 50% of the marks in a given exam). Hence answer is 4 papers where he will score more than 50%.
let total marks for each paper be x.....then total marks in five paper will be 5x...now 3/5 th of it would be 3x....and now the proportions for each paper are 6/40,7/40,8/40,9/40,10/40......now solving it with 3x we get the the marks in each paper and by diividing it by x and multiplying it by 100 we get the percentage...4 are above 50%
Each paper is has the same total marks, so total for each paper is 1/5. You will find that: 6/40 + 7/40 + ... + 10/40 = 1.
We want it to equal 3/5, so divide both sides by 5/3 (as 1/5/3=3/5). This gives you: 18/200 + 21/200 + 24/200 + 27/200 + 30/200 = 3/5.
Because each paper is out of 1/5 you divide each of the proportions in the second line by 1/5. This gives the proportion of marks he got in each test, and from this you can deduce which ones he scored more than 50% in.
Not very algebra-ridden, but I think it makes sense without.
Problem Loading...
Note Loading...
Set Loading...
Let each paper be for 'a' marks...
hence total marks is 5a
ie ... 6x+7x+8x+9x+10x = 3/5 * (5a) (because he obtained 3/5 of the total marks)
therefore 40x = 3a hence x=3a/40
.His total number in 1st paper is = (6*3)a/40 = 0.45(a) ie 45% of a
similarly in 2nd, 3rd, 4th and 5th papers his marks are
52.5% of a , 60% of a, 67.5% of a and 75% of a , respectively .
Clearly he got more than 50% marks in 2nd, 3rd, 4th and 5th papers .
ie he got moer than 50% marks in 4 papers ..... :-)