ABCD is a trapezium, AB is parallel to CD and CD is parallel to EF and AD and BC are non-parallel sides where AD = BC, then which statements (s) is/are correct? A) If E and F are midpoints of side AD and BC respectively, then the length of EF is half of the sum of parallel sides. B) If E and F are not midpoints of sides AD and BC, then EF = (AE × DC + FC × AB)/AD C) If E and F are midpoints of sides AD and BC respectively, then (ar ABFE) : (ar DCFE) = (3AB + DC) : (3DC + AB)
ABCD is a trapezium, AB is parallel to CD and CD is parallel to EF and AD and BC are non-parallel sides where AD = BC, then which statements (s) is/are correct? A) If E and F are midpoints of side AD and BC respectively, then the length of EF is half of the sum of parallel sides. B) If E and F are not midpoints of sides AD and BC, then EF = (AE × DC + FC × AB)/AD C) If E and F are midpoints of sides AD and BC respectively, then (ar ABFE) : (ar DCFE) = (3AB + DC) : (3DC + AB) Correct Answer A, B and C
Given,
ABCD is a trapezium,
AB || CD
CD || EF
AD = BC
Concept:
If △ABC ∼ △PQR, then
AB/PQ = BC/QR = AC/PR
Calculation:
Join A to C, then
In △ABC and ΔPFC
PF/AB = FC/BC
⇒ PF = FC/BC × AB
In △ADC and ΔAEP
EP/DC = AE/AD
⇒ EP = AE/AD × DC
EF = EP + PF
⇒ EF = (AE × DC)/AD + (FC × AB)/BC
⇒ EF = (AE × DC + FC × AB)/AD
Statement B is correct.
If E and F are midpoints, then
AE = ED = AD/2
AE = ED = BF = FC
EF = (AE × DC + AE × AB)/2AE
⇒ EF = /2AE
⇒ EF = (DC + AB)/2
Statement A is correct.
Let height of the trapezium be 2h,
If E and F are two midpoints, then
Height of trapezium ABFE = Height of trapezium DCFE = h cm
Area of trapezium ABFE = (1/2) × (AB + EF) × h
Area of trapezium ABFE = (1/2) × × h
Area of trapezium ABFE = (1/2) × × h
Area of trapezium ABFE = (1/2) × × h
Similarly,
Area of trapezium DCFE = (1/2) × (DC + EF) × h
Area of trapezium DCFE = (1/2) × × h
Area of trapezium DCFE = (1/2) × × h
Area of trapezium DCFE = (1/2) × × h
Area of ABFE : Area of DCFE = (1/2) × × h : (1/2) × × h = (3AB + DC) : (3DC + AB)
∴ All the statements are true.