ICSE-VIII-Mathematics

16: Understanding Shapes (Including Polygons) Class 8 Maths

with Solutions - page 6
  • #4
    Use the information given in the following figure to find : (i) x (ii) ∠B and ∠C
    Answer
    ∵ ∠A = 90˚ (Given)
    ∠B = (2x + 4˚)
    ∠C = (3x - 5˚)
    ∠D = (8x - 15˚)
    ∠A + ∠B + ∠C + ∠D = 360˚
    90˚ + (2x + 4) + (3x - 5) + (8x - 15) = 360
    ⇒ 90 + 2x + 4 + 3x - 5 + 8x - 15 = 360
    ⇒ 74˚ + 13x = 360˚
    ⇒ 13x = 360˚ - 74˚
    ⇒ 13x = 286˚
    ⇒ x = 22˚
    ∵ ∠B = 2x + 4 = 2×22˚ + 4 = 48˚
    ∠C = 3x - 5 = 3 × 22˚ - 5 = 61˚
    Hence (i)22˚ (ii) ∠B = 48˚, ∠C = 61˚