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Mathematics

Assertion (A):

Assertion (A): Assertion Reasoning, Concise Mathematics Solutions ICSE Class 9.

Arc APB : arc APBQC = 5 : 7
and reflex ∠AOC = 210°
then ∠AOB = 150°

Reason (R):

∠AOB=57×reflex AOC\text{∠AOB} = \dfrac{5}{7}\times \text{reflex }∠\text{AOC}
= 57×210°=150°\dfrac{5}{7}\times 210° = 150°

  1. A is true, R is false.
  2. A is false, R is true.
  3. Both A and R are true.
  4. Both A and R are false.

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Answer

Both A and R are true.

Explanation

Arc APB : arc APBQC = 5 : 7

∠ AOB : reflex ∠ AOC = 5 : 7

AOBreflexAOC=57AOB210°=57AOB=5×210°7AOB=5×30°AOB=150°\dfrac{∠ AOB}{\text{reflex} ∠ AOC} = \dfrac{5}{7}\\[1em] \dfrac{∠ AOB}{210°} = \dfrac{5}{7}\\[1em] ∠ AOB = \dfrac{5 \times 210°}{7}\\[1em] ∠ AOB = 5 \times 30°\\[1em] ∠ AOB = 150°

∴ Assertion (A) is true.

As calculated above, ∠AOB=150°\text{∠AOB} = 150°

∴ Reason (R) is true.

Hence, both Assertion (A) and Reason (R) are true.

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