1. Slow and Fast Clocks
By Mdm Lily Hoi

2. Fast clocks Actual time: 09 50
Jack’s clock was 20 minutes fast. He saw that the time was What was the actual time?
Since his clock is fast, it has “gained” 20 minutes.
We need to let it “lose” 20 minutes to get the actual time.
Actual time: 09 50

3. Slow clocks Actual time: 10 30
Jack’s clock was 20 minutes slow. He saw that the time was What was the actual time that Jack woke up?
Since his clock is slow, it has “lost” 20 minutes.
We need to let it “gain back” 20 minutes to get the actual time.
Actual time: 10 30

4. Try it!
Jack’s clock is 20 minutes slow. He woke up one day and saw that the time was What was the actual time?
Since his clock is slow, it has “lost” 20 minutes.
We need to let it “gain back” 20 minutes to get
the actual time.
Actual time: 09 15

5. Try it!
William’s clock is 30 minutes fast. He woke up one day and saw that the time was What was the actual time that William woke up?
Since his clock is fast, it has “gained” 30 minutes.
We need to let it “lose” 30 minutes to get
the actual time.
Actual time: 06 50

6. Challenge yourself! Since her watch “loses” 15 minutes at every hour,
Clara sets her watch correctly at noon. For every actual hour, the watch loses exactly 15 minutes. It now shows What should be the correct time now?
Since her watch “loses” 15 minutes at every hour,
her watch is “slow”.
We need to let it “gain” 15 minutes at every hour to get
the actual time.

7. Challenge yourself! Total lost: 1 hour (15 min x 4) Actual time: 16 00
Clara sets her watch correctly at noon. For every actual hour, the watch loses exactly 15 minutes. It now shows What should be the correct time now?
Clock
Actual
Noon
12 45
13 00
13 30
14 00
14 15
15 00
16 00
Total lost: 1 hour (15 min x 4)
Actual time: 16 00

8. Challenge yourself! Since his clock “gains” 20 minutes at every hour,
Raymond sets his clock correctly at midnight. For every actual hour, the clock gains exactly 20 minutes. It now shows What should be the correct time now?
Since his clock “gains” 20 minutes at every hour,
his clock is “fast”.
We need to let it “lose” 20 minutes at every hour to get
the actual time.

9. Challenge yourself! Total gain: 1 h 20 min (20 min x 4)
Raymond sets his clock correctly at midnight. For every actual hour, the clock gains exactly 20 minutes. It now shows What should be the correct time now?
Clock
Actual
Midnight
01 20
01 00
02 40
02 00
04 00
03 00
05 20
Total gain: 1 h 20 min (20 min x 4)
Actual time: 04 00

10. Challenge yourself! Ans: 23 45 on Monday in Amsterdam
When it was in Singapore, it was in Amsterdam.
At on Tuesday in Singapore, Mr Lee made a call to Amsterdam.
What time and day would it be in Amsterdam?
Between Sg and Amst -> 6 h difference
Time in Amst is slower than Sg. It is 6 h behind Sg time. Time in Sg is faster than Amst.
1h h
Mon Tues Tues
Ans: on Monday in Amsterdam