Slow and Fast Clocks By Mdm Lily Hoi

Fast clocks Jack’s clock was 20 minutes fast. He saw that the time was 10 10. What was the actual time? Since his clock is fast, it has “gained” gained 20 minutes. We need to let it “lose” 20 minutes to get the actual tim Actual time: 09 50

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

Try it! • Jack’s clock is 20 minutes slow. He woke up one day and saw that the time was 08 55. What was the actual time? Since his clock is slow, it has “lost” lost 20 minutes. We need to let it “gain back” 20 minutes to get the actual time. Actual time: 09 15

Try it! • William’s clock is 30 minutes fast. He woke up one day and saw that the time was 07 20. What was the actual time that William woke up? Since his clock is fast, it has “gained” gained 30 minutes. We need to let it “lose” 30 minutes to get the actual time. Actual time: 06 50

Challenge yourself! • Clara sets her watch correctly at noon. For every actual hour, the watch loses exactly 15 minutes. It now shows 15 00. 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.

Challenge yourself! • Clara sets her watch correctly at noon. For every actual hour, the watch loses exactly 15 minutes. It now shows 15 00. 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

Challenge yourself! • Raymond sets his clock correctly at midnight. For every actual hour, the clock gains exactly 20 minutes. It now shows 05 20. 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.

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

Challenge yourself! • When it was 13 20 in Singapore, it was 07 20 in Amsterdam. • At 05 45 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. 1 h 23 45 Mon 5 h 00 45 Tues 05 45 Tues Ans: 23 45 on Monday in Amsterdam