- A29
- B61
- C56
- D59
Step-by-Step Solution
Angles around a point sum to 360°. So → → → . Check: 59 + 128 + 173 = 360. Trap: 29 comes from using 180° as the total , which would only be right if the three angles lay along a straight line.
Answer: D) 59
Three angles meet at a point and measure °, ° and °. Find .
Class 7Lines and AnglesLines and Angles
Key idea: Vertically opposite angles
When two straight lines cross, four angles form at the intersection. The two angles directly **across** the vertex (sharing only the vertex, not a side) are called **vertically opposite** — and they are always equal.
If one angle is 70°, then:
- Its vertical opposite is also 70°.
- The other two angles are each 110° (linear pair with 70°).
Why? Each pair forms a linear pair with a common neighbour, both summing to 180° — so the opposites end up equal.
If one angle is 70°, then:
- Its vertical opposite is also 70°.
- The other two angles are each 110° (linear pair with 70°).
Why? Each pair forms a linear pair with a common neighbour, both summing to 180° — so the opposites end up equal.
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