The Total solution for NCERT class 6-12
In the given figure, if PQ|| ST, ∠PQR =110º and ∠RST =130º, find ∠QRS.
[Hint: Draw a line parallel to STthrough point R.]
Let us draw a line XYparallel to ST and passing through point R.
∠PQR + ∠QRX = 180º (Co-interior angles on the same side of transversal QR)
⇒ 110º + ∠QRX = 180º
⇒ ∠QRX = 70º
Also,
∠RST + ∠SRY = 180º (Co-interior angles on the same side of transversal SR)
130º + ∠SRY = 180º
∠SRY = 50º
XY is astraight line. RQ and RS stand on it.
∴ ∠QRX + ∠QRS + ∠SRY = 180º
70º + ∠QRS + 50º = 180º