Plane Geometry
- If the bisector of an angle of Δ bisects the opposite side, then the Δ is :
-
View Hint View Answer Discuss in Forum
According to given question, ∠1 = ∠2
∴ AB = BD AC AD
Correct Option: B
Since ∠1 = ∠2
∴ AB = BD AC AD
But BD = CD (given)∴ AB = 1 AC
AB = AC
∴ the given ∆ is isosceles
- The areas of two similar Δs are 81 cm2 and 144 cm2. If the largest side of the smaller Δ is 27 cm, then the largest side of the larger Δ is :
-
View Hint View Answer Discuss in Forum
Let ABC and DEF be the two similar Δs having area 81 cm2 and 144 cm2 respectively:
Let BC = 27 cm
Then since ΔABC ∼ ΔDEF∴ area (∆ABC) = BC2 (area Theorem) area (∆DEF) EF2 Correct Option: C
Let ABC and DEF be the two similar Δs having area 81 cm2 and 144 cm2 respectively:
Let BC = 27 cm
Then since ΔABC ∼ ΔDEF∴ ar (∆ABC) = BC2 (area Theorem) ar(∆DEF) EF2 81 = (27)2 ⇒ 9 = 27 144 x2 12 x
∴ x = 36 cm.
- In the given figure ∠BAD = ∠CAD. AB = 4 cm, AC = 5.2 cm, BD = 3 cm. Find BC.
-
View Hint View Answer Discuss in Forum
According to question, Given that
∠BAD = ∠CAD. AB = 4 cm, AC = 5.2 cm, BD = 3 cm
In ΔABC, AD is the bisector of ∠AAB = BD (Internal bisector prop.) AC CD Correct Option: A
According to question, Given that
∠BAD = ∠CAD. AB = 4 cm, AC = 5.2 cm, BD = 3 cm
In ΔABC, AD is the bisector of ∠AAB = BD (Internal bisector prop.) AC CD 4 = 3 ⇒ DC = 3.9 cm 5.2 DC
But BC = BD + CD = 3cm + 3.9 cm = 6.9 cm
- A ladder 15 m long reaches a window which is 9 m above the ground on one side of street. Keeping its foot at the same point, the ladder is turned to the other side of the street to reach a window 12 m high. What is the width of the street:
-
View Hint View Answer Discuss in Forum
Draw a figure as per given question,
In a Right triangle ADC, Use the (Pythagoras Theorem)
AC = √DC2 - AD2
In a Right triangle BCE, Use the (Pythagoras Theorem)
CB = √ CD2 - BE2
Correct Option: D
Draw a figure as per given question,
In a Right triangle ADC, Use the (Pythagoras Theorem)
AC = √DC2 - AD2
⇒ AC = √ 152 - 9 2
⇒ AC = √ 225 - 81
⇒ AC = √ 144
⇒ AC = 12 cm
In a Right triangle BCE, Use the formula
CB = √ CD2 - BE2
⇒ CB = √15 2 - 122
⇒ CB = √225 - 144
⇒ CB = √ 81
⇒ CB = 9 m
∴ Width of the street (AC + BC) = AB = 12 + 9 = 21 m.
- D and E are the points on the sides AB and AC respectively of ΔABC such that AD = 8 cm, BD = 12 cm, AE = 6 cm and EC = 9 cm. Then find BC/ DE.
-
View Hint View Answer Discuss in Forum
Since AD = AE = 2 DB EC 3
∴ DE || BC (by converse of BPT)
∴ ΔADE ∼ ΔABC (AA similarity)
Correct Option: A
Since AD = AE = 2 DB EC 3
∴ DE || BC (by converse of BPT)
∴ ΔADE ∼ ΔABC (AA similarity)AD = DE AB BC 8 = DE AB BC 2 = DE ⇒ BC = 5 5 BC DE 2