Savings: 1 Mark
Amount invested in each company: 1 Mark each
Let total savings = Rs 100
∴ Investment in company X = 20% of 100 = Rs 20
Investment in company Y = 30% of 100 = Rs 30
Investment in company X = 25% of 100 = Rs 25
Now, Income from company X = Rs (10100×20)=Rs 2
Income from company Y = Rs (12100×30) = Rs 3.60
Similarly, income from company Z = Rs (15100×25)=Rs 3.75
Total income = Rs 2 + Rs 3.60 + Rs 3.75 = Rs 9.35
Now, if income is Rs 9.35, then savings = Rs 100
If income is Rs 2,337.50, then savings = Rs (100×2337.509.35) = Rs 25,000
∴ Amount invested in company X = 20% of savings = Rs 20100×25000
= Rs 5000
Amount invested in company Y = 30% of savings = Rs 30100×25000 = Rs 7500
Amount invested in company Z = 25% of savings = Rs 25100×25000 = Rs 6250
Thus, amount invested in companies, X, Y and Z respectively are Rs 5,000, Rs 7,500 and Rs 6,250.