Answer: Naman pulls in the string at the rate of 5 cm per second. Hence, after 12 seconds the length of the string he will pulled is given by: 12 × 5 = 60 cm or 0.6 m In ∆BMC By...
In a ∆ABC, AD is a median and AL ⊥ BC. Prove that
Answer: Adding $\Rightarrow A D^{2}+B C \cdot D L+\left(\frac{B C}{2}\right)^{2}$ and $A B^{2}=A D^{2}-B C-D L+\left(\frac{B C}{2}\right)^{2}$, $\begin{aligned} AC^{2}+A...
In a ∆ABC, AD is a median and AL ⊥ BC. Prove that (i) (ii)
Answers: (i) In right triangle ALD, Using Pythagoras theorem, $A C^{2}=A L^{2}+L C^{2}$ $\Rightarrow A D^{2}-D L^{2}+(D L+D C)^{2}$ $\Rightarrow A D^{2}-D L^{2}+\left(D...
An aeroplane leaves an airport and flies due north at a speed of 1000km per hour. At the same time, another aeroplane leaves the same airport and flies due west at a speed of 1200 km per hour. How far apart will be the two planes after hours?
Answer: Let A be the first aeroplane flied due north at a speed of 1000 km/hr and B be the second aeroplane flied due west at a speed of 1200 km/hr Distance...
ABC is an isosceles triangle, right-angled at B. Similar triangles ACD and ABE are constructed on sides AC and AB. Find the ratio between the areas of ∆ABE and ∆ACD.
Answer: ABC as an isosceles triangle, right angled at B. AB = BC Applying Pythagoras theorem in right-angled triangle ABC, ????????2 = ????????2 + ????????2 = 2????????2...
In ∆ABC, AB = AC. Side BC is produced to D. Prove that ????????2 – ????????2 = BD. CD
Answer: Draw AE⊥BC, meeting BC at D. Applying Pythagoras theorem in right-angled triangle AED, ABC is an isosceles triangle and AE is the altitude and we know that the altitude...
In the given figure, D is the midpoint of side BC and AE⊥BC. If BC = a, AC = b, AB = c, AD = p and AE = h, prove that (i) (ii)
Answers: (i) Adding $b^{2}=p^{2}+a x+\frac{a^{2}}{x}$ and $c^{2}=p^{2}-a x+\frac{a^{2}}{x}$, $b^{2}+c^{2}=p^{2}+a x+\frac{a^{2}}{4}+p^{2}-a x+\frac{a^{2}}{4}$ $b^{2}+c^{2}=2...
In the given figure, D is the midpoint of side BC and AE⊥BC. If BC = a, AC = b, AB = c, AD = p and AE = h, prove that (i) (ii)
Answers: (i) In right-angled triangle AEC, Applying Pythagoras theorem, ????????2 = ????????2 + ????C2 $b^{2}=h^{2}+\left(x+\frac{a}{2}\right)^{2}$ …(1) In right – angled...
In the given figure, CD ⊥ AB Prove that
Answer: Given, ∠???????????? = 90o ???????? ⊥ ????B In ∆ ACB and ∆ CDB ∠???????????? = ∠???????????? = 90o ∠???????????? = ∠???????????? By AA similarity-criterion, ∆ ACB ~ ∆CDB...
In ∆ABC, D is the midpoint of BC and AE⊥BC. If AC>AB, show that
Answer: In right-angled triangle AED, applying Pythagoras theorem, ????????2 = ????????2 + ????????2 … (????) In right-angled triangle AED, applying Pythagoras theorem,...
Find the length of each side of a rhombus whose diagonals are 24cm and 10cm long.
Answer: Let ABCD be the rhombus with diagonals meeting at O. AC = 24 cm BD = 10 cm We know that the diagonals of a rhombus bisect each other at angles. Applying Pythagoras...
Find the length of a diagonal of a rectangle whose adjacent sides are 30cm and 16cm.
Answer: Let ABCD be the rectangle with diagonals AC and BD meeting at O. AB = CD = 30 cm BC = AD = 16 cm Applying Pythagoras theorem in right-angled triangle ABC, we get:...
Find the height of an equilateral triangle of side 12cm.
Answer: Let ABC be the equilateral triangle with AD as an altitude from A meeting BC at D. D will be the midpoint of BC. Applying Pythagoras theorem in right-angled triangle...
∆ABC is an equilateral triangle of side 2a units. Find each of its altitudes.
Answer: Let AD, BE and CF be the altitudes of ∆ABC meeting BC, AC and AB at D, E and F, D, E and F are the midpoint of BC, AC and AB, In right-angled ∆ABD, AB = 2a BD = a...
Find the length of altitude AD of an isosceles ∆ABC in which AB = AC = 2a units and BC = a units.
Answer: In isosceles ∆ ABC, AB = AC = 2a units BC = a unit Let AD be the altitude drawn from A that meets BC at D. D is the midpoint of BC. BD = BC = ????2...
∆ABC is an isosceles triangle with AB = AC = 13cm. The length of altitude from A on BC is 5cm. Find BC.
Answer: Given, ∆ ABC is an isosceles triangle. AB = AC = 13 cm The altitude from A on BC meets BC at D. D is the midpoint of BC. AD = 5 cm ∆ ????????????...
In the given figure, O is a point inside a ∆PQR such that ∠PQR such that ∠POR = 90o, OP = 6cm and OR = 8cm. If PQ = 24cm and QR = 26cm, prove that ∆PQR is right-angled.
Answer: Applying Pythagoras theorem in right-angled triangle POR, ????????2 = ????????2 + ????????2 ????????2 = 62 + 82 =>36 + 64 =>100 ???????? = √100 =>10 ???????? In...
A guy wire attached to a vertical pole of height 18 m is 24m long and has a stake attached to the other end. How far from the base of the pole should the stake be driven so that the wire will be taut?
Answer: Let AB be a guy wire attached to a pole BC of height 18 m. Now, to keep the wire taut let it to be fixed at A. In right triangle ABC By using Pythagoras theorem,...
Two vertical poles of height 9m and 14m stand on a plane ground. If the distance between their feet is 12m, find the distance between their tops.
Answer: Let the two poles be DE and AB and the distance between their bases be BE. DE = 9 m AB = 14 m BE = 12 m Draw a line parallel to BE from D, meeting AB at C. DC = 12 m AC...
A ladder is placed in such a way that its foot is at a distance of 15m from a wall and its top reaches a window 20m above the ground. Find the length of the ladder.
Answer: Let the height of the window from the ground and the distance of the foot of the ladder from the wall be AB and BC, AB = 20 m BC = 15 m Applying Pythagoras theorem in...
A 13m long ladder reaches a window of a building 12m above the ground. Determine the distance of the foot of the ladder from the building.
Answer: Let AB and AC be the ladder and height of the building. Given, AB = 13 m AC = 12 m In right-angled triangle ABC, $A B^{2}=A C^{2}+B C^{2}$ $B...
A man goes 10m due south and then 24m due west. How far is he from the starting point?
Answer: Let the man starts from point D and goes 10 m due south at E. He then goes 24 m due west at F. In right ∆DEF, DE = 10 m EF = 24 m $D F^{2}=E F^{2}+D E^{2}$ $D...
A man goes 80m due east and then 150m due north. How far is he from the starting point?
Answer: Let the man starts from point A and goes 80 m due east to B. From B, he goes 150 m due north to c. In right- angled triangle ABC, $A C^{2}=A B^{2}+B C^{2}$...
The sides of certain triangles are given below. Determine which of them right triangles are (a – 1) cm, 2√???? cm, (a + 1) cm
Answer: Given, The sum of the two sides must be equal to the square of the third side. The three sides of the triangle - a, b and c. P = (a-1) cm, q = 2 √???? ???????? ???????????? ???? = (???? + 1)...
The sides of certain triangles are given below. Determine which of them right triangles are. (i) 1.4cm, 4.8cm, 5cm (ii) 1.6cm, 3.8cm, 4cm
Answers: Given, The sum of the two sides must be equal to the square of the third side. The three sides of the triangle - a, b and c. (i) a = 1.4 cm b= 4.8 cm c= 5 cm ????2 + ????2 = (1.4) 2 + (4.8)...
The sides of certain triangles are given below. Determine which of them right triangles are. (i) 9cm, 16cm, 18cm (ii) 7cm, 24cm, 25cm
Answers: Given, The sum of the two sides must be equal to the square of the third side. The three sides of the triangle - a, b and c. (i) a = 9 cm b = 16 cm c = 18 cm ????2 + ????2 = 92 + 162...