In the diagram, the area of rectangle ABCD is 40. What is the area of MBCN?
Note that
40 = AB * BC
40 = 10 * BC
BC = 4 = AD
Draw MO perpendicular to DC
And MO = BC
Area of rectangle AMOD = AD * AM = 4 * 5 = 20
Area of right triangle MON = (1/2)(BC) (ON) = (1/2)(4)(3) = 6
Area of MBCN = 40 - 20 - 6 = 14
