Maths: Time

In a time question, you might be given two times: when something starts, and when it ends. Then it asks how long that takes, in minutes, or in hours and minutes.

Or it gives you one time, and asks for it another way, like in 24-hour time. Either way, you pick one of five answers.

GL writes times in more than one style: with a colon, with a dot, as four figures, or with am and pm. The video above and the worked example below work through the same question, with the options in the same order. The question after it, where step 1 is the whole question, is the video's second one.

The method

Four steps: line up the times, jump to the next hour, jump the hours and the rest, add the jumps.

Worked example

A cookery class starts at 13:55 and ends at 15:20. How many minutes does it last?

A. 35 minutes B. 75 minutes C. 80 minutes D. 85 minutes E. 165 minutes

1. Line up the times. Picture a time line. Both times are already in 24-hour time, so 13:55 goes on the left, and 15:20 on the right.
2. Jump to the next hour. After 13:55, the next hour is 14:00. 55 up to 60 is 5, so the first jump is 5 minutes. 75 minutes is option B. That adds the minutes, 55 and 20. But 55 is where the class starts, not a jump, so B is out.
3. Jump the hours and the rest. From 14:00, one whole hour takes you to 15:00. Then 20 more minutes reach 15:20. 35 minutes is option A. That's just the gap between 55 and 20. It leaves out the whole hour in the middle, so A is out.
4. Add the jumps. 60 minutes make an hour, so the hour jump is 60 minutes. 5 + 60 + 20 = 85 minutes, and the question asks for minutes. 165 minutes is option E. That takes the times away like ordinary numbers, as if an hour were 100 minutes, so E is out. 80 minutes is option C. That adds only the last two jumps and leaves out the first 5 minutes, so C is out too. So the answer is D.

Answer: D — 85 minutes (5 min + 60 min + 20 min = 85 minutes)

A second worked example: step 1 can be the whole question

Sometimes the first step is the whole question.

A piano lesson starts at quarter to five in the afternoon. What is this time on the 24-hour clock?

A. 04:45 B. 14:45 C. 16:45 D. 17:15 E. 17:45

1. Line up the times. First, the words. "To" means before the hour. Quarter to five means 15 minutes before five, so jump back from 5:00 to 4:45. Then, in the afternoon, add 12 to the hour. 4 + 12 = 16, so it's 16:45. 04:45 leaves the hour as it is, so A is out. 14:45 adds only 10, so B is out. 17:15 and 17:45 are both after five in the afternoon, but quarter to five comes before five, so D and E are out. So the answer is C.

Answer: C — 16:45 (quarter to five = 4:45 · afternoon: 4 + 12 = 16)

Things to watch out for

1. An hour is 60 minutes, not 100. Never take times away like ordinary numbers. A walk starts at 15:35 and ends at 17:15. Taking the times away like ordinary numbers gives 180 minutes, which is three whole hours. But the walk doesn't even last two hours. Count on: 25 minutes, 1 hour, then 15 minutes. That makes 100 minutes.
2. Count up to the next hour first. The first whole hour starts at the next hour. A school trip sets off at 14:50 and gets back at 17:05. Counting 14 to 17 as three whole hours, plus the minutes, gives 3 hours 15 minutes. But the first whole hour only starts at 15:00. 10 minutes to 15:00, two whole hours to 17:00, then 5 minutes: 2 hours 15 minutes.
3. After 12 noon, add 12. Get both times in the same style before you count. A coach leaves at 8:45 am and arrives at 1:40 pm. 1:40 looks earlier than 8:45, and counting back between them gives 7 hours 5 minutes. Add 12 to the afternoon time: 1:40 pm is 13:40. Now count on: 15 minutes, 4 whole hours, then 40 minutes. That's 4 hours 55 minutes.
4. Midnight is just another hour. Count on to midnight, then on again. A ferry sails at 21:25 and docks at 07:30 the next morning. 35 minutes to 22:00, 2 hours to midnight, 7 hours to 07:00, then 30 minutes. That's 9 hours and 65 minutes, and 65 minutes is an hour and 5, so 10 hours 5 minutes. Stopping at midnight, or starting there, leaves part of the crossing out.

Related

• The complete 11+ question-type guide
• Maths: Measures — spot the units and make them the same
• Maths: Reading Graphs and Tables — read the graph first, then work out the scale
• Maths: Word Problems — plan, then finish every step

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