3 mistakes learners make with time problems, each one named and explained.
Time runs in sixties, so never treat minutes as decimals.
Times are added or subtracted as if there were a hundred minutes in an hour.
Every other calculation at school works in tens, and a clock is the one place that does not.
Question. 09:45 plus 2 hours 35 minutes
A common answer. 11:80
The answer. 12:20
Why. 80 minutes is more than an hour, so it becomes 1 hour and 20 minutes.
If your minutes go past 59, carry an hour. A time with 80 minutes in it is never right.
The number of whole hours between two times is one out.
Counting hours across the boundary where the minutes decrease is where this goes wrong.
Question. 14:35 to 16:50
A common answer. 3 hours 15 minutes
The answer. 2 hours 15 minutes
Why. From 14:35 to 16:35 is two hours, and then 15 minutes more.
Jump whole hours first and finish with the minutes. Never do both at once.
An answer is given to the nearest hour when the minutes were asked for.
The hour is the part that feels significant and the minutes look like detail.
Question. 09:45 plus 2 hours 35 minutes
A common answer. 12:00
The answer. 12:20
Why. The 35 minutes has to be added exactly, not rounded.
Times are exact unless the question says about or roughly.
WAJD spots these patterns in your child's answers and names the one behind their wrong answers, instead of just marking them wrong.