Question:
A quadrilateral has three acute angles. If each measures 80°, then the measure of the fourth angle is
(a) 150o
(b) 120o
(c) 105o
(d) 140o
Solution:
(b) 120o
We know that, sum of all interior angle of quadrilaterals is equal to 360o.
Let us assume the fourth angle be x
Then,
80o + 80o + 80o + x = 360o
240o + x = 360o
x = 360o – 240o
x = 120o