hazelnut wrote:

20 students including Tom take a test and Tom gets 5.8 pts higher than their average score. If the teacher gives all the 20 students an additional 10 pts question and Tom is the only one who solved it correctly, how many pts is tom’s average score higher than the average score of the total 20 students?

A. \(6.2\)

B. \(10.4\)

C. \(10.5\)

D. \(15.3\)

E. \(16.2\)

Algebraic approach..

Let x be the average...

So Tom's marks =x+5.8

Now only Tom answers a 10 marks question correctly..

So new total =20x+10 and average = \(\frac{20x+10}{20}=x+0.5\)

Tom's marks now = x+5.8+10=x+15.8

Difference= \(x+15.8-(x+0.5)=15.3\)

D

You can also take x as some value if you are not comfortable with variable x..

Remember x does not effect the question at all, as it gets subtracted out.

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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372

2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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