Mrs Lim started baking at 8.45 a.m. and finished at 11.15 a.m. How long did she spend baking?
Need a hint?
Break the time into parts: count the minutes to the next hour, then count the whole hours, then add the remaining minutes.
Worked answer
- From 8.45 a.m. to 9.00 a.m. is 15 minutes.
- From 9.00 a.m. to 11.00 a.m. is 2 hours.
- From 11.00 a.m. to 11.15 a.m. is 15 minutes.
- Total time = 15 min + 2 h + 15 min = 2 h 30 min.
Answer: 2 h 30 min
The mistake this question tests
Habit
Minutes and hours in rate
Pupils often subtract 8.45 from 11.15 directly as if it were a normal subtraction sum, getting 2.70, then write 2 h 70 min or 3 h 10 min.
How to fix it at home →Wrong answers children often give:
- 3 h 10 min Calculation slip
- 2 h 70 min Minutes and hours in rate
- 2.3 h Minutes and hours in rate
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