Hint
How many minutes are there between 2:00 and 7:00?
Answer
65 minutes.
Reasoning
We need to break down the five hours in the following way:
3 x Answer minutes past two o'clock40 minutesAnswer minutes before seven o'clock
Why? It is now Answer minutes before seven o'clock, and then we have the 40 minutes before that, and the remaining time was 3 x Answer minutes past two o'clock.
So, five hours = 5 x 60 = 300 minutes. We already know about the 40 minutes, so we have to share the remaining 260 minutes in the ratio 3:1, which gives 195:65 minutes. Or using algebra 4 x Answer = 300 − 40, so Answer = 65 minutes.
Therefore, the five hours is made up of:
195 minutes past two o'clock40 minutes65 minutes before seven o'clock
So, it's currently 65 minutes before 7:00 = 5:55.
Double-Checking
It is now 65 minutes before seven o'clock = 5:55, so 40 minutes ago it was 5:15 – which is 195 minutes after 2:00, as required (as 65 x 3 = 195).
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Puzzle 198
Recently Kevin had a party and because it was his birthday he wanted a mathematical cake!
He ordered a cake in the shape of a cube and had it completely iced (but of course the shop didn't ice the underneath because that just isn't very sensible).
He cut every side of the cake into three equal pieces, giving 27 slices of cake.
He ended up eating all of the pieces of cake that had exactly 2 sides with icing.
So, how many pieces did that leave for the guests?