Skip to main content
### Number and algebra

### Geometry and measure

### Probability and statistics

### Working mathematically

### For younger learners

### Advanced mathematics

# Watch the Clock

First we estimated an answer. The answer must be between 2 and 3 on the clock. So it must be between 2:10 and 2:15. Then we worked out how many degrees each hand moves in 1 minute.

The minute hand moves $360\div60=6$ degrees per minute.

The hour hand moves $(360\div12)\div60=0.5$ degrees per minute.

If $T$ is the time in minutes after 2:00 then the minute hand has moved $6T$ degrees.

The hour hand has moved $60+0.5T$

When the hands are pointing in the same direction these must be equal

$6T=60+0.5T$

$5.5T=60$

$T=60\div5.5$

$= 120\div11$

$= 10$ min$+10\div11$ x $60$ sec

= $10$ min $55$ sec (to the nearest second) after 2:00

Or search by topic

Age 7 to 11

Challenge Level

- Problem
- Getting Started
- Student Solutions
- Teachers' Resources

This challenge caused a lot of hard thinking. Some took the time to be around 2.10 and others around 3.15 according to how they interpreted the question. Either way led to some careful working out. The amount the small hour hand moves led to slightly different suggested answers.

Hasa, Javeria and Sarah wrote:

First we estimated an answer. The answer must be between 2 and 3 on the clock. So it must be between 2:10 and 2:15. Then we worked out how many degrees each hand moves in 1 minute.

The minute hand moves $360\div60=6$ degrees per minute.

The hour hand moves $(360\div12)\div60=0.5$ degrees per minute.

If $T$ is the time in minutes after 2:00 then the minute hand has moved $6T$ degrees.

The hour hand has moved $60+0.5T$

When the hands are pointing in the same direction these must be equal

$6T=60+0.5T$

$5.5T=60$

$T=60\div5.5$

$= 120\div11$

$= 10$ min$+10\div11$ x $60$ sec

= $10$ min $55$ sec (to the nearest second) after 2:00

Isobel sent in her suggestion as:

I found out that roughly the answer was 3:17 am. I found this
puzzle quite tricky. So I borrowed my mum's alarm clock and fiddled
with the arms until I found the answer.