Was 70 the average (arithmetic mean) grade on a class test?

Question

(1) On the test, half of the class had grades below 70 and half of the class had grades above 70.
(2) The lowest grade on the test was 45 and the highest grade on the test was 95.

FN · Answer

Hmm E I think...i was struggling between C and E...

(a) is insuff..say half the students score 0 and the other half score 100...

you do not know the distribuition....

(b) it just gives us the range, If we knew the std. Deviation we could get the Avg...

together Insuff..(say in B if all students score 45, and all the other half scored 95....)

gsr · Answer

i think E

We need the number of students in the class and more info. on the grades to find the mean.

nero44 · Answer

Click E --> Click Next --> Click Confirm

There is no way, to find out the average of the information given. 1 & 2 together... could be 50 times grade 45 and then 49 times grade 71 and one time grade 95...... or there could be another distribution, which has an effect on the average.

rahulraao · Answer

Agree! I posted this coz I was calculating the average using B by assuming (for some strange reason) that all the scores inbetween would be evenly placed!

OA is E!

fozzzy · Answer

Is answer choice A.. a trap answer in this question?

Bunuel · Answer

I find nothing too tricky in the first statement.

Was 70 the average (arithmetic mean) grade on a class test?

(1) On the test, half of the class had grades below 70 and half of the class had grades above 70 --> {69, 71} answer YES but {69, 100} answer NO. Not sufficient.

(2) The lowest grade on the test was 45 and the highest grade on the test was 95 --> {45, 95} answer YES but {45, 69, 95} answer NO. Not sufficient.

(1)+(2) {45, 95} answer YES but {45, 69, 95, 95} answer NO. Not sufficient.

Answer: E.

JayBKK · Answer

My thinking is

(1) Median = 70
(2) Min = 45, Max = 95

Can these tell mean = 70? -> Median = (Min + Max)/2

Cannot conclude the mean at 70 from (1) and (2), so choose E.

(However, I got this question wrong by my quick reflex...)

agil31 · Answer

Answer: E

Take cases for each statement and try to get a YES and a NO for the problem statement. 
In S1: 10, 10 , 80, 80 give a no while 60,60,80,80 give a yes - No consistency so INSUFFICIENT
In S2: 45, 65 , 80 , 95 give a no while just 45 and 95 give a yes - No consistency so INSUFFICIENT
Combining both, use the same examples as S2 - INSUFFICIENT

FrozenDragon · Answer

Yes,  A  choice is indeed a trap. To see through the options, we need to understand that there can be multiple scenarios, and in most of them, we won't get the average of 70.

Was 70 the average (arithmetic mean) grade on a class test?

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Was 70 the average (arithmetic mean) grade on a class test?

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