How many kids failed each subject?

• Jun 6th 2011, 02:42 PM
Satnam
How many kids failed each subject?
Out of 42 kids in a class twice as many failed Ela as math,4 failed both. If 7 failed neither, find how many failed each subject.
• Jun 6th 2011, 03:00 PM
HallsofIvy
This is your problem- show some of your work! I recommend a "Venn diagram" that consists of two overlapping circles, one representing the students who passed math, one representing the students who passed Ela (?) If "7 failed neither" there are 7 students in the overlap.
• Jun 6th 2011, 03:25 PM
Satnam
i dont get it still
• Jun 6th 2011, 04:06 PM
mr fantastic
Quote:

Originally Posted by Satnam
i dont get it still

Then you need to say exactly what you tried to do and where you get stuck.

Here is the equation you need to solve:

x + 4 + [2(x+4) - 4] + 7 = 42.

Yes, the equation is useless without a Venn diagram to justify it - your job is to draw the Venn diagram (as suggested - quite helpfully I might add - in post #2) and justify the above equation. However, I'd suggest using circles that represent students who failed (which is what I did).
• Jun 6th 2011, 06:25 PM
Satnam
Out of 42 kids in a class twice as many failed Ela as math,4 failed both. If 7 failed neither,
find how many failed each subject.
I made a venn diagram the middle part of the venn diagram would be 7 and the math part would be 13 and the ela part would be 26. How do i check this?
• Jun 6th 2011, 07:52 PM
mr fantastic
Quote:

Originally Posted by Satnam
Out of 42 kids in a class twice as many failed Ela as math,4 failed both. If 7 failed neither,
find how many failed each subject.
I made a venn diagram the middle part of the venn diagram would be 7 and the math part would be 13 and the ela part would be 26. How do i check this?

The middle part of mine is 4 (see my earlier post for why, and where 4 appears in my equation). Yes, a total of 13 students FAILED maths, and a total of 26 students FAILED Ela. Obviously a good way of checking these answers would be to see if they are consistent with the information given in the question.
• Jun 9th 2011, 10:32 AM
HallsofIvy
As you say, 13 failed math and 26 failed Ela (What is "Ela"? Must be a tough subject!) that would be a total of 13+ 26= 39 except that, since four students failed both that counts those four twice- actually 39- 4= 35 students failed one or the other or both. Since 7 students did not fail either, there are 35+ 7= 42 students total which is what we are told.