Number Systems

It Indian Book called Quantitative Aptitude for CAT By Arun Sharma, well it helps to prepare very well as it is reference book for admission into IIMs. I am actually confused about some of concepts whether we are suppose to divide by increasing powers 7 or 25 175=5*5*7 and in 36 =2*2*2*3*3*5 divide by increasing powers of 5 ? I know the calculations are long sometimes answer choices are given and rarely not.Number systems chapter is very good in this book and because I have studied Maths the Indian way, sometimes its difficult to understand MGMAT books for some concepts when its given easier way here.I think the concepts tested are same for GMAT and IIM-CAT so that can explain Indian people scoring well in Quant, I have not prepared for CAT but referenced MGMAT books earlier but was not easy to grasp everything was more of hit and miss when i solved GMAT questions. GMAT uses more of concepts driven testing where understanding in detail is very important. I am solving exercises for each chapter from here then moving onto GMAT Material.