Quant~14 min read
Arithmetic & DI
Percent, ratio, SI-CI, time-work, time-distance, mensuration.
- x% of y = xy/100. Successive: a + b + ab/100. Population: P(1±r/100)^n.
- Ratio a:b; if A:B = 2:3 and B:C = 4:5, A:C = 8:15. Partnership divides profit in capital × time.
- SI = PRT/100. CI = P(1+R/100)^n − P. Difference CI−SI for 2 years = P(R/100)².
- Time-work: A’s 1 day = 1/a. Together 1/(1/a+1/b). Pipes: inlet +, outlet −.
- Distance = speed × time. Average speed = 2xy/(x+y) for equal distances. Upstream = b−s, downstream = b+s.
- Mensuration: circle πr², 2πr; triangle ½bh, √s(s−a)(s−b)(s−c); cuboid 2(lb+bh+hl); cylinder 2πr(h+r), πr²h; cone ⅓πr²h; sphere 4πr², 4/3πr³.
- DI: read the legend; check units; prefer approximation when options are wide.
Video Lectures & Explanations
Curated educational video lectures explaining this topic for UPSC EPFO