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Home Aptitude Plane Geometry See What Others Are Saying!
  • Question
  • A, B, C are the three angles of a ?. If A ? B = 15° and B ? C = 30°. Then ?A is equal to :


  • Options
  • A. 65°
  • B. 80°
  • C. 75°
  • D. 85°

  • Correct Answer
  • 80° 

    Explanation

    Since A, B and C are the angles of a ?,
    ? A + B + C = 180° .......................................... (1)
    According to question,
    A ? B = 15° ;
    ? A = B + 15°....................................................(2)
    B ? C = 30°;
    ? B = C + 30°;...................................................(3)
    Put the value of B from equation (2) in Equation (1), we will get
    ? A = B + 15°
    A = C + 30° + 15°
    A = C + 45° ........................................................(4)
    From a equation,
    ? A + B + C = 180°
    ? (C + 45°) + (C + 30°) + C = 180°
    ? 3C + 45° + 30° = 180°
    ? 3C = 180° ? 75° = 105°
    ? C = 35° ..........................................................(5)
    From equation (4)
    A = C + 45°
    Put the value of C from equation (5) , we will get
    ? ?A = 35° + 45° = 80°.


  • More questions

    • 1. 
      ?. x 4 ? 227 = 398
      ?. y 2 + 321 = 346

    • Options
    • A. 1
    • B. 2
    • C. 3
    • D. 4
    • Discuss
    • 2. If 6th March, 2005 is Monday, what was the day of the week on 6th March, 2004?

    • Options
    • A. Sunday
    • B. Saturday
    • C. Tuesday
    • D. Wednesday
    • Discuss
    • 3. 1, 4, 9, 16, 23, 25, 36

    • Options
    • A. 9
    • B. 23
    • C. 25
    • D. 36
    • Discuss
    • 4. 
      A sum of money is to be divided equally among P, Q and R in the respective ratio of 5 : 6 : 7 and another sum of money is to be divided between S and T equally. If S got ? 2100 less than P, then how much amount did Q receive?

    • Options
    • A. ? 2500
    • B. ? 2000
    • C. ? 1500
    • D. Couldn't be determined
    • Discuss
    • 5. 
      If a : b = b : c, then ratio a 4 : b 4 is equal to

    • Options
    • A. ac : b2
    • B. a2 : c2
    • C. c2 : a2
    • D. b2 : ac
    • Discuss
    • 6. 
      A man covers half of his journey at 6 km/h and the remaining half at 3 km/h. Find his average speed.

    • Options
    • A. 3 km/h
    • B. 4 km/h
    • C. 4.5 km/h
    • D. 9 km/h
    • Discuss
    • 7. 
      A person can walk a certain distance and drive back in 6 h. He can also walk both ways in 10 h. How much time will he take to drive both ways?

    • Options
    • A. 2 h
    • B. 21/2 h
    • C. 51/2 h
    • D. 4 h
    • Discuss
    • 8. 
      Find the least number by which 175760 be devided to make it a perfect cube.

    • Options
    • A. 10
    • B. 20
    • C. 100
    • D. 5
    • Discuss
    • 9. 
      The roots of the equation x2 + px + q = 0 are equal if :

    • Options
    • A. p2 = 2q
    • B. p2 = 4q
    • C. p2 = - 4q
    • D. p2 = - 2q
    • Discuss
    • 10. 
      Two cubes have volumes in the ratio 1: 27, The ratio of their surface areas is?

    • Options
    • A. 1 : 3
    • B. 1 : 8
    • C. 1 : 9
    • D. 1 : 18
    • Discuss


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