Q48 / 90 · JEE Main 2022 (27 Jul Shift 2) · Mathematics

The angle of elevation of the top P of a vertical tower PQ of height 10 from a point A on the horizontal ground is 45°. Let R be a point on AQ and from a point B, vertically above R, the angle of elevation of P is 60°. If ∠BAQ=30°,AB=d and the area of the trapezium PQRB is α, then the ordered pair d,α is

  • Correct answer
    A
    103-1,25
  • B
    103-1,252
  • C
    103+1,25
  • D
    103+1,252

Solution

As per the given information, the figure would be 

FigureHere, 

RA=dcos30°=3 d2

QR=AQA-RA=10-3 d2

BR=dsin30°=d2

Now tan60°=10-BRQR=10-d210-3 d2

⇒3=20-d20-3d

⇒203-3d=20-d

⇒2d=203-1

⇒d=103-1

Now artrap PQRB=12PQ+BRQR

=1210+d210-3d2

=1210+53-510-15+53

=1253+553-5=1275-25=25

i.e. α=25

Hence, the correct answer is option: 'A'.

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