Ratio and Proportion for Placement Preparation

Ratio and Proportion for Placement Preparation

Ratio and proportion form the foundation of many quantitative aptitude problems in placement exams. Topics like mixtures, partnership, and work distribution all depend on a solid understanding of ratios. These questions test not just calculation ability but logical thinking under the time pressure of a placement test.

Ratio Basics

A ratio compares two quantities of the same type. The ratio a to b means for every a units of the first quantity there are b units of the second. Proportion is the equality of two ratios. If a to b equals c to d, then a multiplied by d equals b multiplied by c. This cross-multiplication property is the primary tool for solving proportion problems quickly.

Combining Ratios

To combine A to B equals 3 to 4 and B to C equals 5 to 6 into a single three-part ratio, make B equal in both. Multiply the first ratio by 5 and the second by 4 to get A to B to C equals 15 to 20 to 24. So A to C equals 15 to 24, which simplifies to 5 to 8.

Solved Example

A sum of Rs. 1200 is divided among A, B, and C in ratio 3 to 4 to 5. Total parts equal 12. A gets 3 divided by 12 times 1200, giving Rs. 300. B gets 4 divided by 12 times 1200, giving Rs. 400. C gets 5 divided by 12 times 1200, giving Rs. 500. Verification: 300 plus 400 plus 500 equals 1200.

Interview Tips

Ratio problems in placement exams frequently involve 3 or more parties. Always convert all ratios to the same base before comparing or combining them. In partnership problems, always check whether time periods differ — if they do, multiply capital by time to find the effective investment ratio for profit sharing. Forgetting this step is the most common error in partnership questions.