The key conversions to know: 60 seconds = 1 minute, 60 minutes = 1 hour, 24 hours = 1 day, 7 days = 1 week. To convert hours to minutes, multiply by 60. To convert minutes to hours, divide by 60. Be careful: decimal hours are not the same as hours and minutes.
Example (a) — Convert 145 minutes to hours and minutes
Step 1
Divide by 60: 145 ÷ 60 = 2 remainder 25
Step 2
Answer: 2 hours 25 minutes
Example (b) — Convert 3.75 hours to hours and minutes
Step 1
Whole hours = 3. Decimal part = 0.75
Step 2
0.75 × 60 = 45 minutes
Answer
3 hours 45 minutes
Rule: To convert decimal hours to minutes, multiply the decimal part by 60. So 0.25 hours = 0.25 × 60 = 15 minutes.
✔ Quick Check timep1 — Units of time and conversion
Question 1 of 10
Calculating Time Durations
You met the count up in stages method for time durations in Lesson 11.6 — Timetables and Schedules. Here we apply it to trickier cases, including durations that span midnight.
Stage 1: count to the next whole hour → Stage 2: count whole hours → Stage 3: remaining minutes
Example — Overnight duration: 22:50 to 01:35
Stage 1
22:50 → 23:00 = 10 minutes
Stage 2
23:00 → 00:00 (midnight) = 1 hour
Stage 3
00:00 → 01:00 = 1 hour
Stage 4
01:00 → 01:35 = 35 minutes
Total
2 hours 45 minutes
Overnight shortcut: Add 24 hours to the end time if it is earlier than the start. Then subtract: 01:35 → 25:35. 25:35 − 22:50 = 2h 45min.
✔ Quick Check timep2 — Calculating time durations
Question 1 of 10
Multi-Step Time Problems
Many real-life time problems have multiple steps. The key is to identify what you are being asked, convert to the right units, and work through each step in order.
Example — Consecutive tasks
Problem
Task A takes 1h 15min. Task B takes 40 min. Starting at 08:30 — when does Task B end?
Step 1
End of Task A: 08:30 + 1h 15min = 09:45
Step 2
End of Task B: 09:45 + 40min = 10:25
Example — Wage calculation
Problem
Paid £11.50/hr, worked 7h 30min. Calculate total pay.
A task takes 45 minutes and starts at 10:20. When does it finish?
Step 1
10:20 + 40 minutes = 11:00
Step 2
11:00 + 5 remaining minutes = 11:05
✔ Quick Check timep3 — Multi-step time problems
Question 1 of 10
Interactive — Timeline Builder
● Start (blue)● End (gold)
Start
08:00
→
End
10:00
=
Duration
2h 0min
Practice: Time Durations
Find the duration in minutes for each. Type your answer, then click Check.
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Question
Answer
Result
1
A train departs at 09:15 and arrives at 11:45. Duration (minutes)?
2
A film starts at 19:30 and ends at 21:50. Duration (minutes)?
3
A flight departs 14:20 and lands 17:05. Duration (minutes)?
4
A meeting starts 10:00 and ends 10:45. Duration (minutes)?
5
A bus leaves 08:50 and arrives 09:35. Duration (minutes)?
6
A night shift starts 22:00 and ends 06:00 the next day. Duration (minutes)?
7
An exam starts 13:15 and ends 15:00. Duration (minutes)?
8
A journey starts 06:40 and ends 08:10. Duration (minutes)?
9
A phone call starts 11:05 and ends 11:52. Duration (minutes)?
10
A concert starts 20:15 and ends 23:00. Duration (minutes)?
⚠ Things to Watch Out For
Time is NOT decimal: 1.5 hours means 1 hour 30 minutes, not 1 hour 5 minutes — always convert the decimal part by multiplying by 60, never just read it as minutes.
Crossing midnight: If the end time is earlier than the start time (e.g. start 23:00, end 02:00), the period has crossed midnight — add 24 hours to the end time before subtracting.
12-hour vs 24-hour clock confusion: Double-check am/pm when converting to or from the 24-hour clock — 3:00 pm is 15:00, not 3:00.
Minutes over 60 during addition: When adding times, if the minutes total 60 or more, carry 1 hour and subtract 60 from the minutes.
Mismatched units in speed calculations: If speed is in mph, time must be in hours (not minutes) before dividing or multiplying — convert first.