Question: The measures of two angles of a triangle is in the ratio 4: 5. If the sum of these two measures is equal to the measure of the third angle. Find the smallest angle.
Options:
A) $ 90{}^\circ $
B) $ 50{}^\circ $
C) $ 10{}^\circ $
D) $ 40{}^\circ $
Show Answer
Answer:
Correct Answer: D
Solution:
- Let the two angles of a triangles be $ 4x $ and $ 5x, $ respectively.
Given, third angle = Sum of these two angles.
Third angle $ =4x+5x=9x $
Sum of the measure of all the angles of a triangle is $ 180{}^\circ . $
$ \therefore $ $ 4x+5x+9x=180{}^\circ $
$ \Rightarrow $ $ 18x=180{}^\circ $
$ \Rightarrow $ $ x=10{}^\circ $
$ \therefore $ Smallest angle $ =4x=4\times 10=40{}^\circ $