ABCD is parallelogram and E is a point on AD, which divides AD in the ...
Given, ABCD is a parallelogram and E is a point on AD dividing AD in the ratio 3:1.
To find: Area of parallelogram ABCD
Approach:
- Draw a perpendicular from B to AD and let it meet AD at F.
- As per the properties of parallelogram, BF is parallel to AC and AD.
- As EF is a line passing through point E, BF and AC, and AD, ∠EBC and ∠FBC are alternate angles and therefore equal.
- Similarly, ∠AFC and ∠BCF are alternate angles and therefore equal.
- Also, ∠ABC and ∠FBE are vertically opposite angles and therefore equal.
- Therefore, ΔEBC and ΔFBM (where M is the midpoint of BC) are similar triangles, as they have two angles equal.
- As E divides AD in the ratio 3:1, we can say that AE:ED = 3:1. Therefore, AM:MD = 3:1.
- As M is the midpoint of BC, BM = MC. Therefore, we can say that BF:FC = 3:1.
Calculation:
- Let the area of triangle EBC be x cm^2.
- As ΔEBC and ΔFBM are similar triangles, we can say that their corresponding sides are in the same ratio.
- Therefore, as BM:MC = 1:1, we can say that EB:BF = 3:1.
- Let the height of parallelogram ABCD be h cm.
- As BF:FC = 3:1, we can say that the height of triangle FBC is h/4.
- Therefore, the area of triangle FBC is (1/2) * BF * (h/4) = (1/8) * BF * h.
- As ΔABC and ΔFBE are similar triangles, we can say that their corresponding sides are in the same ratio.
- Therefore, as AB:BF = 3:1, we can say that the height of triangle FBE is (3/4)h.
- Therefore, the area of triangle FBE is (1/2) * BF * (3/4)h = (3/8) * BF * h.
- As ∠ABC and ∠FBE are equal, we can say that the area of parallelogram ABCD is twice the area of ΔFBE.
- Therefore, the area of parallelogram ABCD = 2 * (3/8) * BF * h = (3/4) * BF * h.
- As E divides AD in the ratio 3:1, we can say that AE:ED = 3:1. Therefore, AE = (3/4)AD and ED = (1/4)AD.
- As BF is parallel to AD, we can say that BF:AD = FC:AD = BF+FC:AD = 1:4.
- Therefore, BF = (1/5)AD and FC = (4/5)AD.
- As the height of parallelogram ABCD is h, we can say that the area of parallelogram ABCD = base * height = AD * h.
- Therefore, the area of parallelogram ABCD = AD * h = (AD