Time Speed Distance Formula and Tricks

📑 On this page

⚡ The short answer

Distance = Speed × Time. Cover the one you want and the other two tell you what to do: Speed = D ÷ T, Time = D ÷ S. Convert first: km/h × 5/18 = m/s, and 1 h 20 min is 1⅓ h, not 1.2 h. The trap: fixed distance makes speed and time inverse, so 25% faster saves only 20% of the time.

🎬 The 30-second story

The ten minutes that turned into eight

“Coaching is 16 km away. At 24 km/h that's 40 minutes. Every. Single. Day.”

🛵

Aarav

Aarav's daily scooter ride, always just late.

“Easy fix. I ride 25% faster, I save 25% of 40. Ten minutes!”

⚡

Aarav

He bumps his speed to 30 km/h.

“16 ÷ 30 is 32 minutes. You saved eight, not ten.”

⏱️

Zoya

Zoya times the new ride on her phone.

“Where did my two minutes go?!”

🤯

Aarav

Still late. Still confused.

Tara's maths: The distance never changed, so speed and time move in opposite directions by the same factor, not the same percentage. Speed × 5/4 means time × 4/5. Four-fifths of 40 is 32 minutes, a saving of 20%, not 25%.

What is the formula for speed, distance and time?

Speed is just a rate: how much distance you eat up per unit of time. 40 km/h means 40 km for every hour you keep going. That's the whole chapter. Distance = Speed × Time, and the other two forms are the same sentence rearranged.

🧮 The formula

One relationship, three questions

🏎️

Speed

km per hour, m per second

⏱️

Time

in the SAME unit as the speed

📍

Distance

S = D ÷ T · T = D ÷ S

It has the same shape as price × quantity = bill. If you can check a food-delivery bill, you can do speed. The only new thing is units, and that's where marks actually go.

How do you convert km/h to m/s, and minutes to hours?

1 km is 1,000 m and 1 hour is 3,600 s. So 1 km/h = 1000/3600 m/s = 5/18 m/s. Going the other way, multiply by 18/5. The m/s number is always smaller; if yours is bigger, you flipped the fraction.

km/h	m/s	Metres per minute	Where you meet it
18	5	300	A brisk cycle
36	10	600	City bus
54	15	900	Highway traffic
72	20	1,200	Express train
90	25	1,500	Fast train (CLAT 2019)

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⚠️ Minutes are not decimals

1 h 20 min is 1⅓ h (20/60), not 1.2 h. 1 h 24 min is 1.4 h, not 1.24 h. Examiners love a 24- or 45-minute time because the lazy decimal gives a clean, wrong option.

How do you solve speed, distance and time questions step by step?

Three moves, every time. Label each number as D, S or T. Match the units before touching a formula. Then ask: which quantity is fixed? That last question is what turns a two-equation slog into a one-line ratio.

✍️ Worked example Warm-up ⏱ 30 sec

School bus speed, two units

Meher's school bus covers 15 km in 25 minutes. What is its speed in km/h and in m/s?

1
Time in hours: 25 ÷ 60 = 5/12 h.
2
Speed = 15 ÷ 5/12 = 15 × 12/5 = 36 km/h.
3
In m/s: 36 × 5/18 = 10 m/s.

Answer: 36 km/h, which is 10 m/s

⚡ Per-minute route

Per minute first: 15 ÷ 25 = 0.6 km a minute. × 60 = 36 km/h.

✍️ Worked example CLAT level ⏱ 60 sec

Late at one speed, early at another

Riding to a fest at 30 km/h, Aarav reaches 10 minutes late. At 40 km/h he would be 5 minutes early. How far is the fest, and what is the right travel time?

1
The two trips differ by 10 + 5 = 15 minutes = 1/4 h. Late and early sit on opposite sides of the target, so add.
2
Time at 30 minus time at 40: D/30 − D/40 = D/120.
3
D/120 = 1/4, so D = 30 km.
4
At 30 km/h that's 60 minutes, 10 minutes late, so the right time is 50 minutes.

Answer: 30 km; on-time travel is 50 minutes

⚡ Product ÷ difference

D = (S₁ × S₂ ÷ difference of speeds) × time gap = (30 × 40 ÷ 10) × 1/4 = 120 × 1/4 = 30 km.

✍️ Worked example Tricky ⏱ 25 sec

Slower by a fraction, late by minutes

Walking at 3/4 of her usual speed, Zoya reaches the library 12 minutes late. What is her usual time for the walk?

1
Distance is fixed, so time scales inversely: speed × 3/4 means time × 4/3.
2
New time = usual + 1/3 of usual. That extra third is the 12 minutes.
3
Usual time = 12 × 3 = 36 minutes. Check: 36 × 4/3 = 48, which is 12 late. ✓

Answer: 36 minutes

⚡ The exam-hall shortcut

Flip the fraction, subtract 1, divide: 12 ÷ (4/3 − 1) = 36.

Why does going faster save less time than you expect?

Fix the distance and speed and time become see-saw partners: one up, the other down, so their product stays put. That's inverse proportion, the same idea as more workers needing fewer days (see direct and inverse proportion). Look at a fixed 60 km ride:

📊 The data

Minutes to cover the same 60 km

20 km/h

180 min

30 km/h

120 min

40 km/h

90 min

60 km/h · triple the speed, one-third the time

60 min

20 → 40 km/h saves 90 minutes. 40 → 60 km/h saves only 30. Each extra km/h buys less time than the last.

Speed changes by	Factor	Time changes by	Rule of thumb
+25%	× 5/4	−20%	Aarav's ride
+50%	× 3/2	−33⅓%	time × 2/3
+100%	× 2	−50%	double speed, half time
−20%	× 4/5	+25%	Rohan's Tuesday, below
−25%	× 3/4	+33⅓%	Zoya's walk above
−50%	× 1/2	+100%	half speed, double time

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📌 The one-line rule

If speed rises by x%, time falls by x ÷ (100 + x) × 100%. Easier: write the change as a fraction and flip it. When time is fixed instead, distance follows speed directly: cycle the same hour at 12 and 18 km/h and the distances are 2 : 3.

🎛️ Try it yourself — change any number

Kabir's van: 45 km in 1 hour 15 minutes

Distance (km) Time (hours, as a decimal)

Speed

36 km/h

In m/s

10 m/s

45 ÷ 1.25 = 36 km/h; × 5/18 = 10 m/s

As set: 36 km/h, or 10 m/s. Now type 1.15 for the time, the lazy reading of 1 h 15 min, and watch the speed jump to about 39.13 km/h. That gap is a wrong option waiting for you.

How does speed, distance and time hide in a CLAT caselet?

CLAT 2019 asked speed directly three times. No post-2020 caselet has been a journey yet, but a delivery route fits the format perfectly. The skill is the usual one: turn the paragraph into a table first. We reuse this caselet below.

Kabir's cloud kitchen uses one rider, Rohan, for its lunch run. On Monday Rohan left the kitchen at 12:00 noon and rode 12 km to a college at 36 km/h. He spent 10 minutes there handing over orders, then rode 6 km to an office park, which took 20 minutes in heavy traffic. From there he rode straight back to the kitchen at 44 km/h, reaching at 1:20 pm.

— A CLAT-style caselet

📊 The data

Rohan's Monday, minute by minute

Leg 1: kitchen → college · 12 km at 36 km/h

20 min

Stop at college · time counts, distance doesn't

10 min

Leg 2: college → office park · 6 km, so 18 km/h

20 min

Leg 3: office park → kitchen · 12:50 to 1:20 at 44 km/h = 22 km

30 min

Timeline: 12:20 arrive college, 12:30 leave, 12:50 office park, 1:20 home. Total 40 km in 80 minutes.

Leg 3 never states its distance. You build it: the clock gives 30 minutes, the speed is 44 km/h, so D = 44 × 1/2 = 22 km. CLAT hands you two of D, S and T per leg, sometimes hidden in clock times. Before you mark cannot be determined, check whether the clock quietly gives you the time.

💡 Averages and overtaking have their own pages

Rohan's whole-trip speed is 40 km in 80 minutes = 30 km/h, not the mean of 36, 18 and 44 (32.67). Why: see average speed. Two things moving at once? See trains, races and relative speed.

Where do students lose marks in speed questions?

✓Mixed units: km/h with metres and seconds. Convert first.
✓Minutes as decimals: 45 minutes is 0.75 h, never 0.45 h.
✓Dropping the stop: a halt adds time but no distance.
✓Late plus early: the gap between the two trips is late + early, not the difference.

How CLAT asked it

📝 Asked in CLAT 2019 · Q54 Speed rising every hour

A car driver increases the average speed of his car by 3 km/hr every hour. The total distance travelled in 7 hours if the distance covered in first hour was 30 km, is

A266 km

B273 km

C280 km

D287 km

Reveal answer + reasoning

Answer: B

There is no official key for 2019; this is our solution. Distance in an hour = that hour's speed × 1 h, so the hourly distances are 30, 33, 36, 39, 42, 45, 48 km. Total = 30 + 33 + … + 48 = 273 km.
Faster: the numbers rise evenly, so their average is the middle one, the 4th hour's 39 km. 7 × 39 = 273. About 25 seconds.

Why the others fail

A — 7 × 38: an average hour of 38 km would need the last hour to be 46 km. It is 30 + 3 × 6 = 48.
C — 7 × 40: needs a last hour of 50 km, which means miscounting the increases.
D — 7 × 41: needs a last hour of 52 km. Seven hours have only six increases after the first.

🧪 CLAT-style practice (not a past question) Building a missing distance

(The cloud-kitchen caselet above.)

How far is the office park from the kitchen by the road Rohan took back?

A13.2 km

B22 km

C29.3 km

DCannot be determined

Reveal answer + reasoning

Answer: B

CLAT-style question, not from a past paper. Run the clock: leg 1 takes 12 ÷ 36 h = 20 min, so 12:20. Add the 10-minute stop: 12:30. Leg 2 takes 20 min: 12:50. He is home at 1:20, so the return takes 30 minutes = 1/2 h. Distance = 44 × 1/2 = 22 km. About 45 seconds.

Why the others fail

A — 44 × 0.30: reads 30 minutes as 0.30 h.
C — Forgets the 10-minute stop, so gives the return 40 minutes: 44 × 2/3 ≈ 29.3 km.
D — The distance isn't stated, but the clock times make it computable.

🧪 CLAT-style practice (not a past question) Slower first leg, new arrival time

(Same caselet.) On Tuesday everything was as on Monday, except that road works cut Rohan's speed on the first leg by 20%.

At what time did Rohan get back to the kitchen on Tuesday?

A1:20 pm

B1:24 pm

C1:25 pm

DCannot be determined

Reveal answer + reasoning

Answer: C

CLAT-style question, not from a past paper. Same 12 km, so speed and time are inverse. Speed × 4/5 means time × 5/4: 20 min becomes 25 min. Everything else is unchanged, so he is 5 minutes later: 1:25 pm. About 20 seconds.

Why the others fail

A — Ignores the slowdown entirely.
B — Adds 20% to the 20-minute leg: 4 minutes. A 20% speed cut stretches time by 25%, not 20%.
D — All the other legs are fixed by the passage, so only leg 1 changes.

💥 Myth vs fact

Myth vs fact

🙅 Myth

Ride 25% faster and you arrive 25% sooner.

Tap to bust it →

✅ Fact

Speed × 5/4 means time × 4/5. You arrive 20% sooner.

🙅 Myth

1 hour 30 minutes is 1.3 hours.

Tap to bust it →

✅ Fact

It's 1.5 hours. Divide the minutes by 60, always.

🙅 Myth

To turn km/h into m/s, multiply by 18/5.

Tap to bust it →

✅ Fact

Multiply by 5/18. The m/s number must come out smaller: 72 km/h is 20 m/s.

🙅 Myth

Average speed is the average of the speeds.

Tap to bust it →

✅ Fact

It's total distance ÷ total time. Rohan's 36, 18 and 44 km/h average to 30 km/h over the trip, not 32.67.

Can you do these five?

🎯 Quick quiz

Five speed, distance and time checks

0 / 5

Meher cycles to tuition at a steady 18 km/h.

Q1. How many metres does she cover in one minute?

Without stops a city bus averages 60 km/h. Including stops it averages 45 km/h.

Q2. For how many minutes does the bus stop each hour?

Kabir's usual drive to the wholesale market takes 60 minutes.

Q3. If he drives 50% faster on the same route, how many minutes does he save?

Rohan drives for 1 hour 24 minutes at 50 km/h.

Q4. How far does he go?

Meher and Zoya cycle for the same length of time, at 12 km/h and 16 km/h. Zoya covers 6 km more.

Q5. How far does Meher cycle?

🎯 Speed, distance and time in a nutshell

D = S × T. Speed is a rate, exactly like price per item.
Convert first: × 5/18 for km/h to m/s; minutes ÷ 60 for hours.
Fixed distance: speed and time are inverse. Flip the factor, don't copy the percentage.
Fixed time: distance follows speed directly.
In a caselet, build a leg-by-leg table and let the clock times fill the gaps.

📎 Formula card

Core: D = S × T; S = D ÷ T; T = D ÷ S
Units: km/h × 5/18 = m/s; m/s × 18/5 = km/h
Fixed distance: S₁ : S₂ = T₂ : T₁
Speed up x%: time falls by x ÷ (100 + x) × 100%
Slow to a/b of usual speed, late by t: usual time = t ÷ (b/a − 1)
Late at S₁, early at S₂: D = S₁S₂ ÷ (S₂ − S₁) × (late + early, in hours)
Average speed: total distance ÷ total time; equal distances: 2ab ÷ (a + b)

Frequently asked questions

What is the formula for speed, distance and time?

Distance equals speed multiplied by time. Rearranged, speed is distance divided by time, and time is distance divided by speed. Keep the units matched: km/h goes with hours and km, m/s with seconds and metres. So a bus covering 15 km in 25 minutes travels at 15 ÷ 5/12 = 36 km/h.

How do you convert km/h to m/s?

Multiply by 5/18, because 1 km is 1,000 metres and 1 hour is 3,600 seconds, and 1000/3600 reduces to 5/18. So 72 km/h is 20 m/s and 90 km/h is 25 m/s. To go back from m/s to km/h, multiply by 18/5. The m/s figure is always the smaller number.

If speed increases by 25%, by how much does time decrease?

By 20%, not 25%. Over a fixed distance, speed and time are inversely proportional. A 25% rise multiplies speed by 5/4, so time is multiplied by 4/5, a 20% fall. The general rule: if speed rises by x%, time falls by x ÷ (100 + x) × 100%. A 50% rise cuts time by a third.

Is speed, distance and time asked in CLAT?

Yes, though less than percentages and ratios. CLAT 2019 had three direct questions on trains, races and a car whose speed rose every hour. Since 2020 Quant has come as caselets, and none so far has been a journey, but a delivery route or commute fits the format easily. The rate logic also powers time and work questions.