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A straight road connects points AA and B.B. Car 11 travels from AA to BB and Car 22 travels from BB to AA, both leaving at the same time. After meeting each other, they take 4545 minutes and 2020 minutes, respectively, to complete their journeys. If Car 11 travels at the speed of 60km/hr60 km/hr, then the speed of Car 2,2, in km/hr, is

Solution

✅ Correct Option: 3

Looking at this problem, I need to find Car 2's speed when two cars meet on a road and then take different times to finish their journeys.

Let me set up what we know:

  • Car 1: goes A→BA \to B at 6060 km/hr, takes 4545 min after meeting to reach BB
  • Car 2: goes B→AB \to A at unknown speed, takes 2020 min after meeting to reach AA
  • Both cars start at the same time

Key insight: When the cars meet, they've been traveling for the same amount of time!

Let me call the meeting point MM, and let t=t = time (in hours) from start until they meet.


At the meeting point MM:

  • Car 1 has traveled: 60t60t km (distance AMAM)
  • Car 2 has traveled: v2tv_2 t km (distance BMBM), where v2v_2 is Car 2's speed

After meeting:

  • Car 1 takes 4545 min =0.75= 0.75 hr to go from MM to BB

So distance MB=60×0.75=45MB = 60 \times 0.75 = 45 km

  • Car 2 takes 2020 min =13= \frac{1}{3} hr to go from MM to AA

So distance MA=v2×13MA = v_2 \times \frac{1}{3} km


The crucial connection:

  • Distance AMAM (what Car 1 already traveled) == Distance MAMA (what Car 2 needs to travel)
  • Distance BMBM (what Car 2 already traveled) == Distance MBMB (what Car 1 needs to travel)

This gives us:

60t=v2360t = \frac{v_2}{3} ... (equation 1)

v2t=45v_2 t = 45 ... (equation 2)


From equation 2: t=45v2t = \frac{45}{v_2}

Substituting into equation 1:

60×45v2=v2360 \times \frac{45}{v_2} = \frac{v_2}{3}

2700v2=v23\frac{2700}{v_2} = \frac{v_2}{3}

2700×3=v222700 \times 3 = v_2^2

8100=v228100 = v_2^2

v2=90v_2 = 90


Therefore, Car 2's speed is 9090 km/hr.

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