XOY is a straight line. Rays OP and OQ are drawn on the same side of it so that $\angle XOP$, $\angle POQ$ and $\angle QOY$ are in the ratio $3 : 4 : 5$. What is $\angle XOP$?

Explanation

1. 01

   The three angles together make the straight angle $XOY = 180^\circ$.

2. 02

   Total parts = $3 + 4 + 5 = 12$, so one part = $180^\circ \div 12 = 15^\circ$.

3. 03

   $\angle XOP = 3 \times 15^\circ = 45^\circ$.