"Oxplains how dot ain't," said Mr. Ribsam, suddenly becoming serious.
The mother was also interested, and looked smilingly toward her bright son. Like every mother, her sympathies went out to him. When Nick told his father that he was in error, the mother felt a thrill of delight; she wanted Nick to get the better of her husband, much as she loved both, and you and I can't blame her.
Nick leaned back in his chair, shoved his hands into his pockets, and looked smilingly at his father and his pipe as he said:
"Suppose, to illustrate, that Philadelphia has just one hundred people. Then, if New York has fifty per cent. more, it must have one hundred and fifty people as its population; that is correct, is it not, father?"
Mr. Ribsam took another puff or two, as if to make sure that his boy was not leading him into a trap, and then he solemnly nodded his head.
"Dot ish so,—dot am,—yaw."
"Then if Philadelphia has one hundred people for its population, New York has one hundred and fifty?"
"Yaw, and Pheelatelphy has feefty per cent. less—yaw, yaw, yaw!"
"Hold on, father,—not so fast. I'm teacher just now, and you mustn't run ahead of me. If you will notice in this problem the per cent. in the first part is based on Philadelphia's population, while in the second part it is based on the population of New York, and since the population of the two cities is different, the per cent. cannot be the same."
"How dot is?" asked Mr. Ribsam, showing eager interest in the reasoning of the boy.