Mathematics
What the section tests
MAH MCA CET Mathematics is a speed-and-accuracy paper built on Class 10–12 quantitative aptitude: percentages, ratio and proportion, averages, profit and loss, simple and compound interest, time–speed–distance, time and work, mixtures, progressions, permutations and combinations, probability, mensuration, and basic coordinate geometry.
Core rules to keep ready
- Percentage change: successive changes of a% and b% give a net change of a + b + ab/100, with signs. A 20% rise then 20% fall leaves 96% of the original, not 100%.
- Ratio: if a:b = 2:3, write a = 2k, b = 3k; substitute to avoid fraction errors.
- Time and work: convert days to work-per-day (1/n). Combined rate is the sum of rates; use LCM to avoid fractions.
- Progressions: AP term a + (n−1)d; sum n/2[2a + (n−1)d]. GP term ar^(n−1); sum a(r^n−1)/(r−1) for r ≠ 1.
- Mensuration: circle area πr², circumference 2πr; sphere volume 4/3πr³; cylinder volume πr²h. Match units before substituting.
Worked example
A shopkeeper marks an article 40% above cost and offers successive discounts of 10% and 5%. Let cost = 100. Marked price = 140. After 10% discount: 140 × 0.90 = 126. After 5%: 126 × 0.95 = 119.70. Profit = 19.70 on cost 100, so 19.7%. Treating the discounts as 15% would give 119, a wrong 19% - the error comes from adding discounts instead of multiplying factors.
Traps that cost marks
- Adding successive percentage changes instead of compounding them.
- Using simple interest in a compound-interest question, or applying CI for a fraction of a year without adjusting the rate.
- Mixing km/h and m/s (multiply by 5/18).
- In probability, ignoring "without replacement" or "at least one".
- In AP/GP, using n instead of n−1 in the exponent or term formula.