73
Calculating with hours and minutes
Textbook: Part 2, lesson 70, pp. 62–63
GoalAdding and subtracting hours and minutes.
New words
to last · davom etishtime interval · vaqt oralig‘ishift · smenachanging into minutes · minutlarga aylantirish
Explanation
We can add and subtract times too: hours with hours, minutes with minutes. 4 h 20 min + 3 h 30 min = 7 h 50 min. If minutes reach 60 or more, change 60 minutes into 1 hour: 30 min + 50 min = 80 min = 1 h 20 min. If the start and end are known, duration = end − start.
Worked examples
An olympiad started at 9:00 and ended at 11:00: it lasted 11 − 9 = 2 hours.
A shift from 8:30 to 14:45 lasts 14:45 − 8:30 = 6 h 15 min.
Class activity
“Time line”: draw a number line from 7:00 to 14:00 on the wall. Children place daily-routine cards (wake up, school, lunch) on it and tell how many hours each lasts.
Practice
1
4 h 20 min + 3 h 30 min = ?
7 h 50 min
2
7 h 50 min − 6 h 10 min = ?
1 h 40 min
3
30 min + 50 min = ? min
80
4
An olympiad started at 9:00 and ended at 11:00. How many hours did it last?
2