Question
A train can cross a bridge and a pole in 7.2 seconds and 4
seconds respectively. The length of the bridge is 80 metres. Find the time taken by train to cross a car which is running in the same direction with a speed of 20 m/sec.Solution
Let the length and the speed of the train be 'x' metres and 'y' m/sec respectively.
When it crosses the bridge,
Or, {(x + 80) / y} = 7.2.................(I)
When it crosses the pole,
Or, (x / y) = 4
So, x = 4y............(II)
Or, 4y + 80 = 7.2y
Or, 80 = 3.2y
So, y = (80 / 3.2) = 25 m/sec
And x = 25 × 4 = 100 metres
So, relative speed of the train w.r.t. the car = 25 - 20 = 5 m/sec
So, required time = (100 / 5) = 20 seconds
- Calculate the value of sin120 o  + cos180 o  + tan225 o .
- If sin 2a = (7/9), then find the value of (sin a + cos a).
If sec A + tan A = 3 then the value of cot A is:
If cosx/siny = n and cosx/cosy = m, then the value of cos 2 y is:
1. m 2 /(m 2 Â + n 2 )
2. 1/(m ...The value of sec2 45˚ + 2 tan 135˚ is –
Find the value of the given trigonometric expression:
(sin 22°cos 68° + cos²22°) × sin 30° + (cos 60°tan 45°) × sec 60°
...
sin2 17˚ + sin2 19˚ + sin2 21˚ + sin2 23˚ + ……… + sin2 77˚ = ?
If tan θ + cot θ = 2 where 0 < θ < 90 ; find the value of tan30 θ + cot 29 θ.
If sec 4A = cosec (3A - 50°), where 4A and 3A are acute angles, find the value of A + 75.
Relevant for Exams:
