Answer:
QR = 17 cm
Explanation:
Δ RST is a 5- 12- 13 triangle with hypotenuse RT = 13 cm , then
TS = 5 cm and PT = 2 × 5 = 10 cm
So PS = 10 + 5 = 15 cm
PS is parallel to the vertical line from vertex Q and intersects the horizontal line projected from SR of length 20 - 12 = 8 cm
Using the right triangle formed calculate QR using Pythagoras' identity
QR² = 15² + 8² = 225 + 64 = 289 ( take square root of both sides )
QR =
= 17