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Aptitude & Reasoning · Question Set
Time, Speed & Distance (incl. Trains & Boats) interview questions for placements and exams.
Questions
14
Included in this set
Subject
Aptitude & Reasoning
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Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for Aptitude & Reasoning.
Closing speed is the sum. Eighty km per hour. Time equals distance over closing speed equals one hundred twenty over eighty equals one point five hours which is one hour thirty minutes.
t = 120 / (30+50) = 1.5 h
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For equal distances, average speed is the harmonic mean. Two a b over a plus b. Two times sixty times forty over one hundred gives forty eight.
Vavg = 2ab/(a+b) = 2×60×40/(60+40) = 48
Speed equals distance over time. One hundred fifty over three gives fifty kilometers per hour.
v = 150/3 = 50 km/h
Speed equals length over time. One hundred twenty over ten equals twelve meters per second. Multiply by three point six gives forty three point two km per hour.
v = 120/10 = 12 m/s ⇒ 12×3.6 = 43.2 km/h
For a platform, cover train plus platform length. Total is three hundred meters. Divide by twelve to get twenty five seconds.
t = (120+180)/12 = 300/12 = 25 s
Relative speed is the sum. Ninety plus fifty four equals one hundred forty four km per hour which is forty meters per second. Total length is three hundred fifty meters. Time is three hundred fifty over forty equals eight point seven five seconds.
v_rel = (90+54)×(1000/3600)=40 m/s; t=350/40=8.75 s
Downstream speed is sum. Twelve plus three equals fifteen km per hour. Time equals distance over speed equals twenty seven over fifteen equals one point eight hours. That is one hour forty eight minutes.
t = 27 / (12+3) = 27/15 = 1.8 h = 1 h 48 m
For same direction, use relative speed. Six minus five equals one meter per second. To gain one lap of four hundred meters, time is four hundred seconds.
t = 400 / (6−5) = 400 s
Total distance is three hundred. Time is two hours plus two hours equals four hours. Average speed equals distance over time equals three hundred over four equals seventy five.
Vavg = (120+180)/(120/60 + 180/90) = 300/4 = 75
Let v be the original speed. 150 over v minus 150 over v minus ten equals minus one half hour. Solve v squared minus ten v minus three thousand equals zero. The positive root is sixty.
150/(v−10) − 150/v = 0.5 ⇒ v^2 −10v −3000=0 ⇒ v=60
To convert km per hour to m per second, multiply by five over eighteen. Fifty four times five over eighteen equals fifteen.
54 × 5/18 = 15 m/s
Time is inversely proportional to speed. New time factor is one over one point two which is zero point eight three three. That is a decrease of one sixth, about sixteen point six seven percent.
Δt% = (1/1.2 − 1)×100 = −16.67%
Upstream speed is difference. Twelve minus three equals nine km per hour. Time equals twenty seven over nine equals three hours.
t = 27 / (12−3) = 27/9 = 3 h
Relative speed is thirty six minus three equals thirty three km per hour. Convert to meters per second for length coverage. Thirty three times five over eighteen equals nine point one six seven. Time equals one hundred fifty divided by nine point one six seven which is about sixteen point four seconds.
v_rel = (36−3)×5/18 = 9.166… m/s ⇒ t = 150/9.166… ≈ 16.4 s