What do we mean by rate? In both these cases we are making a mental comparison of something that is happening, and the length of time that it takes to happen. If the motor-car flies past us going yards per second, a simple bit of mental arithmetic will show us that this is equivalent–while it lasts–to a rate of yards per minute, or over miles per hour.
Now in what sense is it true that a speed of yards per second is the same as yards per minute? Ten yards is not the same as yards, nor is one second the same thing as one minute. What we mean by saying that the rate is the same, is this: that the proportion borne between distance passed over and time taken to pass over it, is the same in both cases.
Take another example. A man may have only a few pounds in his possession, and yet be able to spend money at the rate of millions a year–provided he goes on spending money at that rate for a few minutes only. Suppose you hand a shilling over the counter to pay for some goods; and suppose the operation lasts exactly one second. Then, during that brief operation, you are parting with your money at the rate of shilling per second, which is the same rate as £ per minute, or £ per hour, or £ per day, or £ per year! If you have £ in your pocket, you can go on spending money at the rate of a million a year for just minutes.
It is said that Sandy had not been in London
