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Q.

When a student weighing 45 kgs left a class, the average weight of the remaining 59 students increased by 200 g. What is the average weight of the remaining 59 students?

 A.

57

 B.

56.8

 C.

58.2

 D.

52.2

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Solution:
Option(A) is correct

Let the average weight of the 59 students be $A$.

Therefore, the total weight of the 59 of them will be 59 $A$.

The questions states that when the weight of this student who left is added, the total weight of the class

= $59A + 45$

When this student is also included, the average weight decreases by 0.2 kgs.

 $59A + \dfrac{45}{60} = A - 0.2$

$\Rightarrow 59A + 45 = 60A - 12$

$\Rightarrow 45 + 12 = 60A - 59A$

$\Rightarrow A = \textbf{57}$

Edit: For an alternative solution, check comment by Durga.


(8) Comment(s)


Shivakumar
 ()

divided by 60 for 59A+45 not only for 45



Vijay
 ()

simply,

60*(x-.20)-59x=45;

=>x=45+12=57.



Sanajit Ghosh
 ()

@DURGA's ans is right



Zoha Amjad
 ()

answer is 56.8

0.2 kgs increase means

$0.2*59=11.8$

$11.8+45 = 56.8$



Shanu
 ()

The ans should be 56.8

it can be solved as

$60A-((A-0.2)*59)=45$

so $A(\text{avarage}) = 56.8$



Kiruthi
 ()

ans should be 56.8 because in question they have given increased by 200g but while solving they took it as decreased by 200g so 57


Durga
 ()

Hi ,

The answer is 57 only.

Let say the average of 60 students is $x$.

Total weight $=60*x$

If one man left average should increase 200gr

i.e $\dfrac{200}{1000} =0.2 \text{ kg}$

So, $60 \times x-45=59(x+0.2)$

$60x-59x=59*0.2+45$

$\Rightarrow x=56.8 \text{ kg}$

But here we need to calculate the average of 59 students

i.e $56.8+0.2= \textbf{57 kg}$


Elmira
 ()

Thank you for creating a very informative website, much appreciate it.

Please review the solution once again, when multiplying the sides by 60, 59A was left without effect, therefore I think the response is wrong. Oh maybe I am missing something here.

Please explain.

Elmira