10
Review: time
Textbook: Part 1, lesson 10, pp. 31–33
GoalReview units of time (hour, minute, second, day) and operations with time.
New words
day (24 hours) · sutkahour · soatminute · minutsecond · sekund
Explanation
1 day = 24 h, 1 h = 60 min, 1 min = 60 s. To add compound times, add hours to hours, minutes to minutes and seconds to seconds; if a total reaches 60, carry to the next unit. In subtraction, if needed, break 1 hour into 60 minutes. To change to a smaller unit multiply by 60 (or by 24 for days to hours).
Worked examples
3 h 38 min 27 s + 1 h 15 min 24 s = 4 h 53 min 51 s.
6 h 05 min − 2 h 40 min: 6 h 05 min = 5 h 65 min, and 5 h 65 min − 2 h 40 min = 3 h 25 min.
Class activity
“My day”: children write their after-school plan in hours and minutes and work out how long the whole plan lasts.
Practice
1
How many minutes is 3 h 20 min?
200
2
How many hours are in 5 days?
120
3
A trip began at 8:30 and lasted 4 h 45 min. At what time did it end?
13:15
4
A concert lasted 1 h 45 min and the break 15 min. How many minutes is that altogether?
120