Linear Function: Boarding House Expenses

CAT 1999 Slot 1 · Quantitative Ability · Easy · Arithmetic

This is an easy Quantitative Ability question from the CAT 1999 Slot 1 paper. It tests Arithmetic. The full answer key and a step-by-step explanation are below — try it yourself first, then reveal the solution.

Total expenses of a boarding house are partly fixed and partly varying linearly with the number of boarders. The average expense per boarder is Rs. 700\text{Rs. } 700 when there are 2525 boarders and Rs. 600\text{Rs. } 600 when there are 5050 boarders. What is the average expense per boarder when there are 100100 boarders?

  1. A.

    550

  2. B.

    580

  3. C.

    540

  4. D.

    570

Answer

A

Explanation

Let total expense E=F+nVE = F + nV. For n=25n = 25: 25×700=17500=F+25V25 \times 700 = 17500 = F + 25V. For n=50n = 50: 50×600=30000=F+50V50 \times 600 = 30000 = F + 50V. Subtracting: 25V=12500    V=50025V = 12500 \implies V = 500. Then F=1750025(500)=5000F = 17500 - 25(500) = 5000. For n=100n = 100: Total expense = 5000+100(500)=550005000 + 100(500) = 55000. Average expense per boarder = 55000100=550\frac{55000}{100} = 550.

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