White to play, and mate in four moves.
QUICK CALCULATION
Few people know a very singular but simple method of calculating rapidly how much any given number of pence a day amounts to in a year. The rule is this:—Set down the given number of pence as pounds; under this place its half, and under that the result of the number of original pence multiplied always by five. Take, for example, 7d a day:—
| £7 | 0 | 0 |
| 3 | 10 | 0 |
| 2 | 11 | |
| £10 | 12 | 11 |
The reason for this is evident as soon as we remember that the 365 days of a year may be split up into 240, 120, and 5, and that 240 happens to be the number of pence in a pound.
SCIENCE AT PLAY
No. LVIII.—THE GEARED WHEELS
A small wheel with ten teeth is geared into a large fixed wheel which has forty teeth. This small wheel, with an arrow mark on its highest cog, is revolved completely round the large wheel. How often during its course is the arrow pointing directly upwards? Here is a diagram of the starting position.
