78
Parts of quantities (practice)
Textbook: Part 3, lesson 78, pp. 22–24
GoalShares of time units: hour, minute, second, day; finding parts of a number in time problems.
New words
hour · soatminute · minutsecond · sekundday (24 hours) · sutka
Explanation
1 hour = 60 minutes, so 1 minute = 1/60 of an hour. 1 minute = 60 seconds. 1 day = 24 hours, so 1 hour = 1/24 of a day. To find a part of a time, divide by the denominator and multiply by the numerator: 3/4 of an hour = 60 : 4 × 3 = 45 minutes.
Worked examples
1/3 of a day: 24 : 3 = 8 hours.
1/6 of an hour is 60 : 6 = 10 minutes; 5/6 of an hour is 10 × 5 = 50 minutes.
Class activity
“Parts of the clock”: on a large model clock, children show 1/4, 1/2 and 3/4 of an hour with the minute hand and say how many minutes that is.
Practice
1
How many minutes is 1/4 of an hour?
15
2
How many hours is 2/3 of a day?
16
3
A sports session lasts 40 minutes and 3/8 of it is for running. How many minutes is the running?
15
4
A film lasts 2 hours and 1/4 of it has passed. How many minutes have passed?
30
5
It is 1 500 m from the park to the stadium. Nilufar cycled 2/5 of the way at 150 m/min and the rest at 100 m/min. How many minutes did she need?
13