Area of bounded quadrilateral

CAT 2023 Slot 2 · Quantitative Ability · Medium · Coordinate Geometry

The area of the quadrilateral bounded by the Y-axis, the line x=5x = 5, and the lines ∣x−y∣−∣x−5∣=2|x - y| - |x - 5| = 2, is

Answer

45

Explanation

The region is bounded between x=0x = 0 (Y-axis) and x=5x = 5.

For 0≤x≤50 \le x \le 5, we have ∣x−5∣=5−x|x - 5| = 5 - x.

Substitute this into the given equation: ∣x−y∣−(5−x)=2  ⟹  ∣x−y∣=7−x|x - y| - (5 - x) = 2 \implies |x - y| = 7 - x

This gives two linear boundary functions for yy:

  1. x−y=7−x  ⟹  y=2x−7x - y = 7 - x \implies y = 2x - 7
  2. x−y=−(7−x)  ⟹  y=7x - y = -(7 - x) \implies y = 7

Thus, the region is bounded by x=0,x=5,y=7,x = 0, x = 5, y = 7, and y=2x−7y = 2x - 7.

At x=0x = 0, yy ranges from −7-7 to 77 (vertical length =14= 14). At x=5x = 5, yy ranges from 33 to 77 (vertical length =4= 4).

This forms a trapezoid with parallel vertical sides of lengths 1414 and 44, and width 55. Area=14+42×5=9×5=45\text{Area} = \frac{14 + 4}{2} \times 5 = 9 \times 5 = 45

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