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The 24-hour clock, journey times, and adding minutes without writing 14:73.
Question 1 of 12
A train leaves Sevenoaks at 09:00 and arrives in Lisburn at 11:40. How long does the journey take?
Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 09:00 to 09:00 is 60 minutes. From 09:00 to 11:00 is 2 hours. Then 40 more minutes to 11:40. Altogether that is 2 hours 40 minutes. A number line with the two times marked on it turns this into an easy question.
The answer is B. Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 09:00 to 09:00 is 60 minutes. From 09:00 to 11:00 is 2 hours. Then 40 more minutes to 11:40. Altogether that is 2 hours 40 minutes. A number line with the two times marked on it turns this into an easy question.
A bus leaves Dorking at 17:42. It takes 8 minutes to reach Alnwick, a further 10 minutes to Colchester, and another 10 minutes to Falmouth. At what time does it arrive at Falmouth?
Add the legs one at a time rather than totalling them first — it keeps the hour changes visible. 17:42 + 8 minutes = 17:50. + 10 minutes = 18:00. + 10 minutes = 18:10. The whole journey takes 28 minutes. Write each arrival time down as you go rather than holding them in your head.
The answer is C. Add the legs one at a time rather than totalling them first — it keeps the hour changes visible. 17:42 + 8 minutes = 17:50. + 10 minutes = 18:00. + 10 minutes = 18:10. The whole journey takes 28 minutes. Write each arrival time down as you go rather than holding them in your head.
A train leaves Sevenoaks at 12:05 and arrives in Truro at 14:50. How long does the journey take?
Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 12:05 to 13:00 is 55 minutes. From 13:00 to 14:00 is 1 hours. Then 50 more minutes to 14:50. Altogether that is 2 hours 45 minutes. An hour is 60 minutes, not 100. Column subtraction on times is the classic trap.
The answer is B. Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 12:05 to 13:00 is 55 minutes. From 13:00 to 14:00 is 1 hours. Then 50 more minutes to 14:50. Altogether that is 2 hours 45 minutes. An hour is 60 minutes, not 100. Column subtraction on times is the classic trap.
A train leaves Poole at 17:00 and arrives in Colchester at 18:25. How long does the journey take?
Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 17:00 to 17:00 is 60 minutes. From 17:00 to 18:00 is 1 hours. Then 25 more minutes to 18:25. Altogether that is 1 hour 25 minutes. A number line with the two times marked on it turns this into an easy question.
The answer is B. Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 17:00 to 17:00 is 60 minutes. From 17:00 to 18:00 is 1 hours. Then 25 more minutes to 18:25. Altogether that is 1 hour 25 minutes. A number line with the two times marked on it turns this into an easy question.
A bus leaves Dorking at 11:18. It takes 22 minutes to reach Harrogate, a further 27 minutes to Lisburn, and another 18 minutes to Wigan. At what time does it arrive at Wigan?
Add the legs one at a time rather than totalling them first — it keeps the hour changes visible. 11:18 + 22 minutes = 11:40. + 27 minutes = 12:07. + 18 minutes = 12:25. The whole journey takes 67 minutes, which is 1 hour 7 minutes. Write each arrival time down as you go rather than holding them in your head.
The answer is B. Add the legs one at a time rather than totalling them first — it keeps the hour changes visible. 11:18 + 22 minutes = 11:40. + 27 minutes = 12:07. + 18 minutes = 12:25. The whole journey takes 67 minutes, which is 1 hour 7 minutes. Write each arrival time down as you go rather than holding them in your head.
A train leaves Harrogate at 08:05 and arrives in Shrewsbury at 08:55. How long does the journey take?
Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 08:05 to 09:00 is 55 minutes. From 09:00 to 08:00 is -1 hours. Then 55 more minutes to 08:55. Altogether that is 0 hours 50 minutes. An hour is 60 minutes, not 100. Column subtraction on times is the classic trap.
The answer is C. Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 08:05 to 09:00 is 55 minutes. From 09:00 to 08:00 is -1 hours. Then 55 more minutes to 08:55. Altogether that is 0 hours 50 minutes. An hour is 60 minutes, not 100. Column subtraction on times is the classic trap.
A bus leaves Harrogate at 08:48. It takes 24 minutes to reach Barnsley, a further 21 minutes to Truro, and another 14 minutes to Shrewsbury. At what time does it arrive at Shrewsbury?
Add the legs one at a time rather than totalling them first — it keeps the hour changes visible. 08:48 + 24 minutes = 09:12. + 21 minutes = 09:33. + 14 minutes = 09:47. The whole journey takes 59 minutes. When the minutes pass 60, take 60 off and add an hour. Never write a time like 14:73.
The answer is D. Add the legs one at a time rather than totalling them first — it keeps the hour changes visible. 08:48 + 24 minutes = 09:12. + 21 minutes = 09:33. + 14 minutes = 09:47. The whole journey takes 59 minutes. When the minutes pass 60, take 60 off and add an hour. Never write a time like 14:73.
A train leaves Barnsley at 18:55 and arrives in Ilkley at 21:10. How long does the journey take?
Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 18:55 to 19:00 is 5 minutes. From 19:00 to 21:00 is 2 hours. Then 10 more minutes to 21:10. Altogether that is 2 hours 15 minutes. Count up to the next whole hour, then in hours, then the last few minutes. It never goes wrong.
The answer is D. Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 18:55 to 19:00 is 5 minutes. From 19:00 to 21:00 is 2 hours. Then 10 more minutes to 21:10. Altogether that is 2 hours 15 minutes. Count up to the next whole hour, then in hours, then the last few minutes. It never goes wrong.
A train leaves Harrogate at 18:50 and arrives in Alnwick at 20:55. How long does the journey take?
Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 18:50 to 19:00 is 10 minutes. From 19:00 to 20:00 is 1 hours. Then 55 more minutes to 20:55. Altogether that is 2 hours 5 minutes. A number line with the two times marked on it turns this into an easy question.
The answer is D. Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 18:50 to 19:00 is 10 minutes. From 19:00 to 20:00 is 1 hours. Then 55 more minutes to 20:55. Altogether that is 2 hours 5 minutes. A number line with the two times marked on it turns this into an easy question.
A train leaves Stirling at 20:10 and arrives in Falmouth at 22:10. How long does the journey take?
Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 20:10 to 21:00 is 50 minutes. From 21:00 to 22:00 is 1 hours. Then 10 more minutes to 22:10. Altogether that is 2 hours 0 minutes. An hour is 60 minutes, not 100. Column subtraction on times is the classic trap.
The answer is D. Time is not decimal, so subtracting the digits as though they were ordinary numbers goes wrong. Count on instead. From 20:10 to 21:00 is 50 minutes. From 21:00 to 22:00 is 1 hours. Then 10 more minutes to 22:10. Altogether that is 2 hours 0 minutes. An hour is 60 minutes, not 100. Column subtraction on times is the classic trap.
A bus leaves Stirling at 10:03. It takes 12 minutes to reach Alnwick, a further 23 minutes to Ilkley, and another 20 minutes to Kendal. At what time does it arrive at Kendal?
Add the legs one at a time rather than totalling them first — it keeps the hour changes visible. 10:03 + 12 minutes = 10:15. + 23 minutes = 10:38. + 20 minutes = 10:58. The whole journey takes 55 minutes. Add each leg separately. Totalling the minutes first works, but it hides the point where the hour rolls over.
The answer is C. Add the legs one at a time rather than totalling them first — it keeps the hour changes visible. 10:03 + 12 minutes = 10:15. + 23 minutes = 10:38. + 20 minutes = 10:58. The whole journey takes 55 minutes. Add each leg separately. Totalling the minutes first works, but it hides the point where the hour rolls over.
A bus leaves Alnwick at 10:33. It takes 17 minutes to reach Kendal, a further 19 minutes to Lisburn, and another 14 minutes to Stirling. At what time does it arrive at Stirling?
Add the legs one at a time rather than totalling them first — it keeps the hour changes visible. 10:33 + 17 minutes = 10:50. + 19 minutes = 11:09. + 14 minutes = 11:23. The whole journey takes 50 minutes. Write each arrival time down as you go rather than holding them in your head.
The answer is D. Add the legs one at a time rather than totalling them first — it keeps the hour changes visible. 10:33 + 17 minutes = 10:50. + 19 minutes = 11:09. + 14 minutes = 11:23. The whole journey takes 50 minutes. Write each arrival time down as you go rather than holding them in your head.
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