Q. 34.2( 32 Votes )
A girl of height 90 cm is walking away from the base of a lamp post at a speed of 1.2m/sec. If the lamp post is 3.6 m above the ground, find the length of her shadow after 4 seconds.
Given, a girl with height 90cm and speed 1.2m/sec
And the lamp post is 3.6m above
Need to find the length of her shadow after 4sec
Consider Δ ABC and Δ DEC
⇒ ∠ ABC = ∠ DEC = 90°
⇒ ∠ ACB = ∠ DCE
⇒ Δ ABC ∼ Δ DEC
⇒ By converse proportionality theorem if a line divides any two sides of a triangle in the same ratio then the line must be parallel to the third side.
⇒ we have
⇒ x + 4.8 = 4x
⇒ 4x – x = 4.8
⇒ 3x = 4.8
⇒ X =
⇒ X = 1.6m
CE = 1.6m
Hence, the length of her shadow after 4 sec is 1.6m
Rate this question :
In the given figure, AB||CD||EF. given AB = 7.5 cm, DC = ycm, EF = 4.5cm, BC = x cm. Calculate the values of x and y.
In the given figure, DE||OQ and DF||OR. Show that EF||QR.
A girl of height 90 cm is walking away from the base of a lamp post at a speed of 1.2m/sec. If the lamp post is 3.6 m above the ground, find the length of her shadow after 4 seconds.AP- Mathematics
Given that Δ ABC ∼ Δ PQR, CM and RN are respectively the medians of Δ ABC and Δ PQR Prove that
i. Δ AMC ∼ Δ PNR
iii. ΔCMB ∼ ΔRNQ
In the given figure, ∠ADE = ∠B
i. Show that ΔABC ~ ΔADE
ii. If AD = 3.8cm, AE = 3.6 cm, BE = 2.1cm, BC = 4.2cm. find DE.
ABD is a triangle right angled at A and AC ⊥ BD
i. AB2 = BC . BD
ii. AC2 = BC . DC
iii. AD2 = BD . CD
Diagonals AC and BD of a trapezium ABCD with AB||DC intersect each other at the point ‘O’. Using the criterion of similarity for two triangles, show thatAP- Mathematics
Prove that a line joining the midpoints of any two sides of a triangle is parallel to the third side. (Using converse of basic proportionality theorem)AP- Mathematics