Standard Mathematics Primary 4 Geometry

ABCD is a rectangle. E is a point on side BC. A line is drawn from A to E. Given that ∠BAE = 25°, find ∠AEC.

A 25°
B 115°
C 155°
D 65°
Show Worked Solution

Worked Solution

Step 1: Identify the right angle in the rectangle. ABCD is a rectangle, so ∠ABE = 90° (E lies on side BC, and B is a corner). Step 2: Apply the angle sum of triangle ABE. ∠BAE + ∠ABE + ∠AEB = 180°. 25° + 90° + ∠AEB = 180°, so ∠AEB = 65°. Step 3: Use the straight line BC. B, E and C lie on the same straight side, so ∠AEB and ∠AEC are angles on a straight line. ∠AEB + ∠AEC = 180°. Step 4: Solve for ∠AEC. ∠AEC = 180° − 65° = 115°. Answer: 115°

Correct answer: 115°

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