The word ‘circumference’ comes from the Latin word circumferre, meaning to “carry around”. How does the Latin meaning help you define the circumference of a circle? Now, draw CL || AD Then ALCD is a parallelogram So AL = CD = 20 cm and CL = AD = 26 cm. In ∆CLB, we have CL = CB = 26 cm Therefore, ∆CLB is an isosceles triangle. Draw altitude CM of ∆CLB. Since ∆ CLB is an isosceles triangle. So, CM is also the median. 1 1 Then LM = MB = BL = × 20 cm = 10 cm 2 2 [as BL = AB – AL = (40 – 20) cm = 20 cm]. Applying Pythagoras theorem in ∆CLM, we have CL2 = CM2 + LM2 262 = CM2 + 102 CM2 = 262 – 102 = (26 – 10) (26 + 10) = 16 × 36 = 576 CM = 576 = 24 cm Hence, the area of the trapezium = (sum of parallel sides) × Height = (20 + 40) × 24 = 30 × 24 = 720 cm2.
Show answer
c