he interrupt him further. Nevertheless she felt his
large spectacles upon her. And presently he astonished her by saying,
resignedly--doubtless he had decided that thus could the virginal calm
be most surely and swiftly restored:--

"Bring me your book. I will solve your problem."

"Oh!" said Fifi, choking down a cough. And then, "Do you know all about
algebra, too?"

It seemed that Mr. Queed in his younger days had once made quite a
specialty of mathematics, both lower, like Fifi's, and also far higher.
The child's polite demurs were firmly overridden. Soon she was
established in a chair at his side, the book open on the table between
them.

"Indicate the problem," said Mr. Queed.

Fifi indicated it: No. 71 of the collection of stickers known as
Miscellaneous Review. It read as follows:

71. A laborer having built 105 rods of stone fence, found that if
he had built 2 rods less a day he would have been 6 days longer in
completing the job. How many rods a day did he build?

Queed read this through once and announced: "He built seven rods a day."

Fifi stared. "Why--how in the world, Mr Queed--"

"Let us see if I am right. Proceed. Read me what you have written down."

"Let _x_ equal the number of rods he built each day," began Fifi
bravely.

"Proceed."

"Then _105_ divided by _x_ equals number of days consumed. And _105_
divided by _x - 2_ equals number of days consumed, if he had built _2_
rods less a day."

"Of course."

"And (_105_ / _x - 2_) + _6_ = number of days consumed if it had taken
him six days longer."

"Nothing of the sort."

Fifi coughed. "I don't see why, exactly."

"When the text says 'six days longer,' it means longer than what?"

"Why--longer than ever."

"Doubtless. But you must state it in terms of the problem."

"In terms of the problem," murmured Fifi, her red-brown head bowed over
the bewildering book--"in terms of the problem."

"Of course," said her teacher, "there is but one thing which longer can
mean; that is longer than the original rate of progress. Yet you add the
six to the time required under the new rate of progress."

"I--I'm really afraid I don't quite see. I'm dreadfully stupid, I
know--"

"Take it this way then. You have set down here two facts. One fact is
the number of days necessary under the old rate of progress; the other
is the number of days necessary under the new rate. Now what is the
difference between them?"

"Why--isn't that