Read the Clocks
Read the puzzle
Four analogue clocks are numbered 1 to 4. Clock 1 has the hour hand just past 3 and the minute hand on 2, showing 3:10. Clock 2 has the minute hand on 9 and the hour hand most of the way from 4 to 5, showing 4:45. Clock 3 has the minute hand on 4 and the hour hand between 6 and 7, showing 6:20. Clock 4 shows only a question mark. What time does clock 4 show?
What time does clock 4 show?
almost
7:55
Each clock is 1 hour 35 minutes later.
How to solve it
Step one: read each clock carefully. Clock 1 reads 3:10, clock 2 reads 4:45 and clock 3 reads 6:20. On clock 3 the short hand is between 6 and 7 and the long hand is on 4, so it is 6:20, not 4:30.
Step two: find the gap. From 3:10 to 4:10 is 1 hour, and from 4:10 to 4:45 is 35 minutes, so the gap is 1 hour 35 minutes. Check it on the next pair: 4:45 plus 1 hour is 5:45, and 5:45 plus 35 minutes is 6:20. The gap holds.
Step three: add it once more. 6:20 plus 1 hour is 7:20, and 7:20 plus 35 minutes is 7:55. Clock 4 shows 7:55, which is five minutes to eight.
The usual slip is treating the times like ordinary decimals: 3.10 to 4.45 looks like a jump of 1.35, but 4.45 plus 1.35 gives 6.80, which is not a time. Minutes roll over at 60, so add hours and minutes separately.
Quick check: work backwards. 7:55 minus 1 hour 35 minutes is 6:20, matching clock 3.
Learn the method: Number Sequence Puzzles: How to Find What Comes Next
