164.
If when a dealer in curios sold a vase for £119, his profit per cent., and the cost price of the vase, were expressed by the same number, it had cost him £70.
165.
The chance of throwing at least one ace in a single throw with a pair of dice is 11⁄36, for there are five ways in which each dice can be thrown so as not to give an ace, so that twenty-five possible throws exclude aces. Hence the chance of not throwing an ace is 25⁄36, which leaves 11⁄36 in favour of it.
166.
The policeman who ran after a thief starting four minutes later, and running one-third faster, if they both ran straight along the road, caught him in twelve minutes.