Can someone help me on my thought process please? My test is in 2 day and I've spent over 2 hours trying to figure out where I went wrong.....
So my thought process is as follows,
Let the one's who failed in both Math and English be
P---------------Math Pass---------Math Fail--------Total
---Eng Pass-----X---------------Dontknow--------9X
---Eng Fail---Dontknow-----------
P--------Dontknow
Total-----------8X--------------Dontknow---------100
so per the table equation,
population of Math Pass and Eng Fail is ( 8X - X ) =
7Xpopulation of Engl Pass and Math Fail is ( 9X - X ) =
8XTherefore my table is now populated as,
---------------Math Pass---------Math Fail--------Total
---Eng Pass-----X---------------
8X--------------9X
---Eng Fail-------
7X---------------
P--------
7X+
PTotal------------8X--------------
8X+
P-------100
And therefore going by the equations, I get
16X + P = 100
Now lets go to (1)
(1) More than 4 students passed in both the tests.
X>4, so by substituting X=5, P = 20 and life is good........
Substituting X=6, P = 4 and life is good again......
So (A) is IN-sufficient !
Now lets go to (2)
(2) Less than 6 students passed in both the tests.
X<6, so by substituting X = 5, 4, 3, 2, 1 it all gives an OK result; so (B) is IN-sufficient !
Taking (1) and (2) together gives us X=5;
Therefore answer should be (C) as both are needed to give a unique solution

------- doesn't match OA !