MENTAL ARITHMETIC
97. “Now, boys!” said Dr Tripos, “I think of a number, add 3, divide by 2, add 8, multiply by 2, subtract 2, and thus arrive at twice the number I thought of.” What was it?
98.
Two club friends, A and B, deposit similar stakes with C, and agree that whoever first wins three games at billiards shall take the whole of them. A wins two games and B wins one. Upon this they determine to divide the stakes in proper shares. How must this division be arranged?
99.
Not so simple as it sounds is the following compact little problem:—If I run by motor from London to Brighton at 10 miles an hour, and return over the same course at 15 miles an hour, what is my average speed?