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The salaries of Ramesh, Ganesh and Rajesh were in the ratio 6:5:76:5:7 in 20102010, and in the ratio 3:4:33:4:3 in 20152015. If Ramesh's salary increased by 25%25\% during 2010−20152010-2015, then the percentage increase in Rajesh's salary during this period is closest to:

Solution

✅ Correct Option: 2

When we have ratios like 6:5:76:5:7, we can represent the actual salaries using a common multiplier.

In 2010: Let's say the salaries are 6x6x, 5x5x, and 7x7x respectively

Ramesh: 6x6x

Ganesh: 5x5x

Rajesh: 7x7x

In 2015: Similarly, let's say the salaries are 3y3y, 4y4y, and 3y3y respectively

Ramesh: 3y3y

Ganesh: 4y4y

Rajesh: 3y3y

The variables xx and yy represent the "unit value" for each time period. This lets us work with the ratios while keeping track of actual salary amounts.


We're told Ramesh's salary increased by 25% from 2010 to 2015.

Ramesh's salary in 2010: 6x6x

Ramesh's salary in 2015: 3y3y

Since there's a 25% increase: 3y=6x×1.25=7.5x3y = 6x \times 1.25 = 7.5x

Therefore: y=2.5xy = 2.5x

By finding the relationship between xx and yy, we can now compare salaries across the two time periods.


Rajesh's salary in 2010: 7x7x

Rajesh's salary in 2015: 3y=3(2.5x)=7.5x3y = 3(2.5x) = 7.5x

Percentage increase formula: New Value−Old ValueOld Value×100\tfrac{\text{New Value} - \text{Old Value}}{\text{Old Value}} \times 100

Rajesh's percentage increase:

7.5x−7x7x×100=0.5x7x×100=0.57×100\tfrac{7.5x - 7x}{7x} \times 100 = \tfrac{0.5x}{7x} \times 100 = \tfrac{0.5}{7} \times 100

=114×100=7.14%= \tfrac{1}{14} \times 100 = 7.14\%


The percentage increase in Rajesh's salary is approximately 7%.

This method we use with ratio multipliers works for any ratio problem where we need to compare values across different time periods. We always look for the "bridge" information (like Ramesh's 25% increase here) to connect the two scenarios.

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