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  • Brainly User
2014-09-13T10:58:42+05:30
Students passed in both Eng and Math = 75%                 ---(1)
==> Students passed in Eng only = 80% - 75% = 5%      ----(2)
Also students passed in Math only = 85% - 75% = 10% -----(3)
Total of (1) , (2) and (3) = 75%+5%+10% = 90%
Remaining students failed = 100% - 90% = 10%.
10% , i.e., (10/100) of total students who failed = 40
==> Total students = 40 x(100 / 10) = 400  
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thanks i got it easy, but, how the last step comes as =40x(100/10) it should be 40x(10/100) as it is 10%. please explain.
Start with last but one line.
10% ,i.e., (10/100) of (total students who failed ) = 40. It means if there were F students who failed, then 10% of N or (10/100) x N = 40. OR 10xN = 40x100. OR N = (40x100) / 10. [ It is 10% of Total student who failed AND NOT 10% of 40.] Hope it clears doubt. If not, say so. Will try to explain with other examples,please.
Correction to above, F should be N. If there were N students who failed.