A patterned design is painted on the void deck floor at Priya's HDB block. Four straight lines meet at a central point, forming four angles going around the point. Three of the angles measure 90°, 90°, and 40°. The fourth angle is labelled x. How many right angles are there among the four angles, and what is the value of x?
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Worked Solution
Step 1: Use the angle-at-a-point property.
All angles around a point add up to 360°.
90° + 90° + 40° + x = 360°
Step 2: Find the sum of the known angles.
90 + 90 + 40 = 220°
Step 3: Solve for x.
x = 360° − 220° = 140°
Step 4: Identify which angles are right angles.
A right angle is exactly 90°.
The four angles are: 90°, 90°, 40°, and 140°.
Only the two 90° angles are right angles.
There are 2 right angles, and x = 140°.
Correct answer: 2 right angles, x = 140°
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