Advanced Mathematics Primary 5 Angles

Four angles meet at a point O. The angles are (2m + 20)°, (m + 10)°, 3m°, and 90°. Find the value of the angle (2m + 20)°.

A 80°
B 90°
C 100°
D 120°
Show Worked Solution

Worked Solution

Step 1: All angles at a point sum to 360°. (2m + 20) + (m + 10) + 3m + 90 = 360 Step 2: Collect like terms. 6m + 120 = 360 Step 3: Solve for m. 6m = 360 − 120 = 240 m = 40 Step 4: Find the required angle. (2m + 20)° = 2(40) + 20 = 80 + 20 = 100° Check: 100 + (40 + 10) + 3(40) + 90 = 100 + 50 + 120 + 90 = 360° ✓ Answer: 100° Answer: 100°

Correct answer: 100°

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