time and distance Model Questions & Answers, Practice Test for ibps clerk prelims 2024

Answer: (a)

Average speed of two object when distance is same

Average speed = ${2v_1v_2}/{v_1 + v_2}$

Here $v_1$ = x km/h. $v_2$ = y km/h = ${2 × xy}/{x + y}$.

Answer: (c)

Let the speed of a train be v m/s and length of the train be x m.

when crosses telegraph t = 8s

Time = ${\text"Distance"}/{\text"Speed"}⇒8 = x/v$

⇒x = 8 v ...(i)

When crosses bridge

t = 24s, Speed = v

Distance = x + 200 ∵ Time = ${\text"Distance"}/{\text"Speed"}$

∴ 24 = ${x + 200}/v$ ⇒24v = x + 200

⇒24v = 8v + 200 [from eq. (i)]

⇒16v = 200⇒v = ${25}/2$

From eq. (i) x = 8v = 8 × ${25}/2$ = 100 m

Answer: (a)

Let the speed of train = x km/hr

Distance of train = 225 m = ${225}/{1000}$ km

Time taken = 9 sec = $9/{3600}$ hr

Speed of man = 5 km/hr

Relative speed = Speed of train + speed of man

= (x + 5) km/hr

But relative speed = ${{225}/{1000}}/{9/{3600}}$ km/hr

= ${225}/{9 × 1000}$ × 3600 = 90km/hr

⇒x + 5 = 90⇒x = 85 km/hr

∴ Option (c) is correct

Answer: (b)

We are given that A gives B a start of 8 m. This means B starts from the point where A finishes its 8 m. therefore B covers 92 m.

Given that A runs at 6 km/hr.

i.e. A runs at ${6 × 1000m}/{60 min}$ = 100m/min

It is also given that even after giving B a start of 8 m, A reaches early than B by 9 seconds.

Therefore, if A takes 60 sec to complete 100 m race, then B takes (60 + 9) seconds i.e. 69 seconds to complete 92 m.

$D/T = {92}/{69}m/s = {92}/{69} × {18}/5 = {24}/5$ km/hr = 4.8km/hr

Answer: (e)

Suppose the speed of boat in still water is x km/h and speed of stream is y km/h

Speed of boat in downstream = (x + y) km/h

∴ x + y = 32 .... (i)

Speed of boat in downstream = (x – y) km/h

∴ x – y = 28 .... (ii)

Add. Eqs. (i) and (ii), we get

2x = 60

x = 30 km/h