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In September, the incomes of Kamal, Amal and Vimal are in the ratio 8:6:58 : 6 : 5. They rent a house together, and Kamal pays 15%15\%, Amal pays 12%12\% and Vimal pays 18%18\% of their respective incomes to cover the total house rent in that month. In October, the house rent remains unchanged while their incomes increase by 10%10\%, 12%12\% and 15%15\%, respectively. In October, the percentage of their total income that will be paid as house rent, is nearest to

Solution

✅ Correct Option: 1

Let their September incomes be 8k8k, 6k6k, and 5k5k respectively, where kk is some positive number.


Each person pays a percentage of their income toward rent:

Kamal pays: 15%15\% of 8k=15100×8k=1.2k8k = \tfrac{15}{100} \times 8k = 1.2k

Amal pays: 12%12\% of 6k=12100×6k=0.72k6k = \tfrac{12}{100} \times 6k = 0.72k

Vimal pays: 18%18\% of 5k=18100×5k=0.9k5k = \tfrac{18}{100} \times 5k = 0.9k

Total house rent = 1.2k+0.72k+0.9k=2.82k1.2k + 0.72k + 0.9k = 2.82k

The house rent stays the same in October, so this 2.82k2.82k amount remains constant.


PersonSept% IncreaseMultiplierOctober
Kamal$8k10%1.10$8.8k
Amal$6k12%1.12$6.72k
Vimal$5k15%1.15$5.75k
Total$21.27k

Now we have:

  • House rent (unchanged): 2.82k2.82k
  • Total income in October: 21.27k21.27k

Percentage formula: PartWhole×100\tfrac{\text{Part}}{\text{Whole}} \times 100

Percentage = 2.82k21.27k×100\tfrac{2.82k}{21.27k} \times 100

Percentage = 2.8221.27×100\tfrac{2.82}{21.27} \times 100

2.8221.27=0.1326...\tfrac{2.82}{21.27} = 0.1326...

Therefore: 0.1326×100=13.26%0.1326 \times 100 = 13.26\%


This makes intuitive sense: their incomes all increased, but the rent stayed the same, so rent should represent a smaller percentage of their total income compared to September.

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