Hi Azad Khan,
I am a present IPM student and I will give you some small tips which may be helpful.
Talking about the interview you need to current affairs not necessarily worldwide but at least national. You need to learn to be extremely confident and smart in tackling your questions. There are certain math questions also asked. Majorly your confidence is the base. All the best!!
It has three section. First section was the integer type maths question with no negative marks. Second section was of multiple choice maths with negative marks. Third section was also MCQs from English with negative marking system.
The maths questions demanded more your aptitude than your memory formulas. So develop your IQ and try to solve a lot of mental maths daily.
Being strong in mental maths will save your lot of time.Yes a calculator was provided in the top right corner but only for the second section. Also it did not function properly,got jammed and had to restart the calculator everytime you do a single operation.
Second many questions were from logarithms which was my strong section ,so be thorough in logarithms.
Do many types of maths questions involving reasoning because many questions will involve resoning ability.
Try to solve maths questions daily. Yes time is very limited and you have to speed up your brains in the test as fixed period of time is alloted to each section and after the time gets over the next section will automatically be switched over and you cannot return to the previous section. This speed will only be there within you if you practice questions daily.
Third is the English section. Questions were moderate level for me,though some of my friends felt the options confusing. Yes all the options will seem as if they all are correct. So you have to stick to your own thinking and answer that only.I feel that one month or a less preparation is enough for it but you can read daily newspapers. Depends on how good you are in speaking fluent English. Yes if you are a good speaker then automatically the correct words will come to your mind.
Read idioms,phrases, synonyms,antonyms,homonyms e.t.c . Questions ask these things also.
Read newspapers daily.Since two to three comprehension paragraph will be coming . Most of the questions will be related to the paragraph. So develop your reading speed and efficiency. So reading newspapers will surely enhance your reading speed.