Architecture

scale drawings, map ratios, structural load distribution

Map ratios like "1:50000" tell you 1 cm on paper = 500 m in reality. Architects scale floor plans the same way at 1:100 or 1:50.

Cooking

recipe scaling — doubling or halving ingredient quantities

Indian kitchens know "rice : water = 1 : 2" ratio. Doubling guests means doubling both — the proportion stays fixed.

Finance

P/E ratio, debt-to-equity ratio, portfolio allocation

P/E ratio (price ÷ earnings) tells investors how many years of profits they're paying for. A P/E of 30 = paying 30 years of current earnings.

Medicine

drug dosage proportional to body weight

Paracetamol dose for kids is 10–15 mg per kg body weight — a strict ratio. Get it wrong and you risk overdose.

Photography

aspect ratio, sensor crop factor

Phone cameras shoot at 16:9 aspect ratio for video, 4:3 for photos, 1:1 for Instagram. The ratio determines the sensor crop.

Exams

ubiquitous in CAT, SSC, Bank, GMAT quantitative sections

Partnership profit splits, mixture-and-alligation, and direct/inverse variation are core CAT/Bank topics — all built on cross-multiplication.