A pupils mark was wrongly entered as 83 instead of 63 . Due to that, the average marks of the class got increased by 0.5. The number of pupils in the class is?
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.
increase in total marks due to error is 20.......per person increase is 0.5...so total number of pupil 20/0.5=40
Log in to reply
I did the same way, but didn't know how to explain. I just wrote the solution like that, little bit confusing I guess. Well, thanks for it!
"the average increased by half" implies that if the average before was x, then the new average is 1.5x, it would be better to state, 0.5 is added to the average to avoid the confusion
Wonderfull :-)
total students =y total marks =x (when score was calculated by taking 83 marks) average marks =x/y but the real arks were 63 ie 20 less than 83 therefore x-20/y=x/y-1/2(when score was 83 average was more by half a mark so now it will be less by half a mark) therefore solving the above equation x-20=x-y/2 -20=-y/2 y=40
I thought the average doubled. That's why I gave wrong Answer.
penis=chode so i like cock
nice problem
2 0 = 0 . 5 n n = 0 . 5 2 0 n = 4 0 EASIEST WAY
An explanation, for your thought process , to arrive at such a crisp solution is appreciated .
why 20=0.5*no of student ?? i cant understand ... please explain
I JUST DO THIS METHOD AND FIND THE CORRECT ANSWER 83-63/0.5
X:average: N:pupils numbers X+0.5=83/N, X=(83-0.5N)/N X=63/N (83-0.5N)/N=63/N, 83-0.5N=63, 0.5N=20, N=40
[(x+20)/N - x/N] = 0.5, where, x = initial total marks, N = No of pupil & solve for N.. {x will cancelled out}
Let y be the total marks of all the students in the class. Let the number of students be x.
We can do it in a simple way:
let total no. of students = n; then,
n (83) - n (63) = n (0.5) Solve to get n = 40.
20/y=0.5 , where y is no of students.. Implies y= 20/.5= 40
There is difference of 83-63 =20 marks to give avg higher by 0.5 therefore number of pupil in the class = 20/0.5 that is 40 Ans K.K.GARG,India
Let the total students be x & average marks be y. Case 1 : 83/x =y + 0.5 Case 2 : 63/x = y Subtracting Case 2 from Case 1, we get value of x i.e. 40
Just doubled the percentage increase 0.5 by 2 to make it 1. And similarly doubled marks too. Was surprised to see the answer was correct :D
Problem Loading...
Note Loading...
Set Loading...
Assume that the sum of all marks except the wrong entered is a, the total number of pupils is n. Then,
n a + 8 3 = n a + 6 3 + 2 1 since if we entered 83, the average increased by half.
n a + 8 3 − n a + 6 3 = 2 1
n a + 8 3 − a − 6 3 = 2 1
n 2 0 = 2 1
n = 4 0