Answer:
1). AC=8.25cm
2). DB=7cm & EC=14cm
3). See Explanation
Explanation:
According To the Question,
Given That, In ∆ABC, D and E are points on the sides AB and AC respectively such that DE is parallel to BC.
1). If AD= 2.5 cm ,BD = 3cm ,AE = 3.75 cm find length of AC.
Well we can apply Basic proportionality Theorem.
Since DE ║ BC ⇒ Sides are proportional and the angles are equal.
⇒ AD / BD = AE / EC
⇒ 2.5 / 3 = 3.75 / EC
On Solving we get,
⇒ EC * 2.5 = 3.75 * 3
⇒ EC * 2.5 = 11.25
⇒ EC = 11.25 / 2.5
⇒ EC = 4.5 cm
Thus,
AC = AE + EC
⇒ AC = 3.75 + 4.50
⇒ AC = 8.25 cm
Hence the measure of AC is 8.5 cm.
2). If AD = 4 cm , AE =8cm ,DB =x – 4 cm ,EC =3x -19 cm
Well we can apply Basic proportionality Theorem.
Since DE ║ BC ⇒ Sides are proportional and the angles are equal.
⇒ AD / BD = AE / EC
⇒ 4 / (x-4) = 8 / (3x-19)
on solving we get,
⇒ 3x-19 = 2(x-4)
⇒ 3x-19 = 2x-8
⇒x=11
Thus, DB =x–4 ⇒ 11-4 ⇒ DB=7cm
And, EC =3x-19 ⇒ 3×11-19 ⇒ EC=14cm
3). If AD=2cm , BD= 4cm , show that BC = 3 DE
Thus, AB = AD + DB = 2+4 = 6cm
Well we can apply Basic proportionality Theorem.
Since DE ║ BC ⇒ Sides are proportional and the angles are equal.
⇒ AD/AB = DE / BC
⇒ 2 / 6 = DE / BC
on solving we get
⇒ BC = 3 DE Hence, Proved