In the given figure, angle Q is a right angle. PS : QS = 3 : 1, RT : QT = 5 : 2, and PU : UR = 1 : 1. If the area of triangle QTS is 20 cm^2, then the area of triangle PQR in cm^2 is ______.

GATE 2015 · General Aptitude · Triangles · medium

Answer: Area of triangle PQR = 280 cm^2

  1. Find QS/QP from PS:QS = 3:1: QS/(QS+PS) = 1/(1+3) = 1/4. So QP/QS = 4.
  2. Find QT/QR from RT:QT = 5:2: QT/(QT+RT) = 2/(2+5) = 2/7. So QR/QT = 7/2.
  3. Write area ratio using the right-angle property: = (1/4) * (2/7) = 2/28 = 1/14
  4. Solve for area(PQR): area(PQR) = 14 * 20 = 280 cm^2