Time measurement
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There are two sand timers which can show 7 minutes and 4 minutes respectively. Measure time of 9 minutes using both.
1. Start both the timers
2. Once 4-min timer ends, flip it
Elapsed Time – 4 minutes
3. Once 7-min timer ends, flip it. There will be 1 min. remaining in 4-min timer.
Elapsed Time – 7 minutes
4. Once 4-min timer ends, there will be 6 min. remaining in 7-min timer. Flip 7-min timer
Elapsed Time – 8 minutes
5. When 7-min timer ends, total elapsed time will be 9 minutes.
Your Answer
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