It is essential for MBA aspirant to be crystal clear on fundamentals. Most of the MBA entrance examinations like CAT, XAT, NMAT, MAT, CMAT, IIFT & SNAP etc. are testing you in data interpretation / quantitative analysis.
DI and QA cannot be cleared until you are not thorough with arithmetic and algebra of 10th standard. You need to be good in mental math also. Hence, you can practice with NCERT books and later with mock tests.
Likewise logical reasoning and verbal ability can also be cleared if you are good in vocabulary, grammar, composition and framing of sentences. This can be achieved only with practice.
Essay writing is the ultimate in written test as you need to be perfect in written communication and expression of thoughts.
With the above it is obvious that having clarity on fundamentals of math, English and general awareness will only succeed you for achieving mission admission MBA.