Grade 3 lesson
Find elapsed time by making smaller jumps
Do not try to hold the whole interval in your head. Start at the given time, jump to the next hour, then count the minutes that are left.
Find the ending time
Reading time
When does it end?
Example: 3:47 plus 38 minutes
- Count 13 minutes from 3:47 to 4:00.
- There are 25 minutes left because 38 - 13 = 25.
- Count 25 more minutes from 4:00. The ending time is 4:25.
Why the next hour helps
An hour boundary is an easy stopping point. Splitting 38 minutes into 13 and 25 is usually easier than counting all 38 marks one at a time.
When the interval is longer than an hour
Take out each full hour first. For example, 74 minutes is 60 minutes plus 14 minutes. Move the hour hand forward once, then count 14 minute marks.
Check the answer
Ask whether the ending time should be later or earlier than the start. Then estimate. If about 40 minutes pass after 3:47, an answer near 4:30 is reasonable; 3:25 is not.
Keep exact-minute reading fresh
Elapsed-time work is much easier when the starting time can be read without hesitation.