The CSAT paper has become the biggest hurdle for many deserving candidates. You don’t need to score 150+; you just need a safe 80+ to cross the 66-mark qualifying threshold. Here are high-yield concepts you must memorize.
1. Number System (Most Important)
UPSC is obsessed with Number System, Remainders, and Divisibility Rules.
- Divisibility by 8: The last 3 digits of the number must be divisible by 8.
- Divisibility by 9: The sum of the digits must be divisible by 9.
- Divisibility by 11: The difference between the sum of digits at odd places and even places is either 0 or a multiple of 11.
2. Time, Speed, and Distance
- Relative Speed: When two objects move in the same direction, Relative Speed = |S1 – S2|. When moving in opposite directions, Relative Speed = S1 + S2.
- Average Speed: If a person travels a certain distance at ‘x’ km/hr and returns at ‘y’ km/hr, Average Speed = (2xy) / (x + y).
3. Permutation & Combination (P&C)
P&C questions have increased exponentially. Remember:
- Permutation (Arrangement matters): nPr = n! / (n-r)!
- Combination (Selection only): nCr = n! / [r! * (n-r)!]
Pro Tip: Do not let ego drive your CSAT attempt. If a math puzzle takes more than 3 minutes, skip it. Pick the low-hanging fruits first.