Best Book for CSAT maths is M Tyra + previous year upsc and PPSC questions
But Still Always there are some questions in Paper those don’t require to solve by proper method But anybody can judge answer by Reading carefully both questions and Options Such questions are designed to check ability of aspirant Quickness sharpness of mind here i am posting some such questions and their explanation to solve them quickly without touching pen or writing a single word less then 10 seconds .
1.UPSC Prelims 2015
In given question ratio of income is given and and income have to be find out .As ratio is 4:3 income should be divisible by 4 and 3 respectively .this eliminates 4h option . then subtracting 6000 from each income will give expenses so those values should be divisible by 3 and 2 respectively only A fulfills this criteria . So answer is A .
2.PCS Prelim 2013
At 3 PM minutes hand will be at 12 and hours hand at 3. they will meet between 3 and 4 .So minute hand must move at least 15 minutes to pass 3 . only option here more then 15 is D so answer is D .
3.PCS 2013 Prelims
simplest ONE . obtained marks are asked and difference is given 9 .only option satisfy it is A . so answer is A .
4.PCS 2013 Prelims
Age of Anand is asked here as ratio of present is 5:4 .Anand’s age should be divisible by 4 . we left with two options only a and c . then after adding 3 it should be divisible by 9 .only a satisfy this condition .
5.UPSC Prelim 2015
At 6PM hour hand at 6 and minutes hand at 12. to be ahead by three minutes hour hand will definitely before 7 and hour hand will be by max at 38 only options fulfills condition is C.
6.PCS Prelim 2013
By divisibility Rule 1176 is divisible only by 3 .So we left with only option a or b as q can not be more then 1. using again divisibility rule 1176 is divisible by 8. so p is 3 .and answer is B .v
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