It seems to be the stereotype that there are Literature People and Math People, and never the twain shall meet. This isn't entirely true, though. While I skew more toward the literary, I generally got good grades in math, and found it pretty interesting. Perhaps that's one reason I'm such a fan of Lewis Carroll's works, as he played with both words and mathematical concepts in his writings. Another childhood favorite of mine, Norton Juster's The Phantom Tollbooth, presented words and numbers as being of equal importance. L. Frank Baum and Ruth Plumly Thompson, however, don't strike me as having been especially mathematically minded people. Take, for instance, this exchange in Chapter 19 of Land, involving the wishing pills:
"Not unless we can count seventeen by twos," answered the Tin Woodman. "But our friend the Woggle-Bug claims to be highly educated, so he ought easily to figure out how that can be done."
"It isn't a question of education," returned the Insect; "it's merely a question of mathematics. I've seen the professor work lots of sums on the blackboard, and he claimed anything could be done with x's and y's and a's, and such things, by mixing them up with plenty of plusses and minuses and equals, and so forth. But he never said anything, so far as I can remember, about counting up to the odd number of seventeen by the even numbers of twos."
"Stop! stop!" cried the Pumpkinhead. "You're making my head ache."
"And mine," added the Scarecrow. "Your mathematics seem to me very like a bottle of mixed pickles the more you fish for what you want the less chance you have of getting it. I am certain that if the thing can be accomplished at all, it is in a very simple manner."
Shortly after this, the party decides to use the Sawhorse's suggestion, which is to start at one-half, then double it and count by twos from one to seventeen, which is mathematical nonsense as far as I can tell. It's been discussed on Oz forums several times, and one suggestion I remember is that the doubling and then counting is based on an archaic formula, but I don't know of any evidence to support this. The pills work anyway, however, but maybe they just ignore the superfluous one-half at the beginning. Or perhaps, as suggested in Wooglet in Oz, adding that to the count was what made Tip's stomach ache after swallowing one of the pills.
As for Thompson, there's this bit of dialogue in Chapter 17 of Grampa in Oz:
"That's fair enough," agreed Percy Vere, smiling at the little flower fairy:
"You believe in us, and we'll believe in you.
And if you say so I'll believe that six and one are--are--?"
"Two," said Dorothy, "only they're eight."
Is this a mistake on Thompson's part, or did she mean to have Dorothy also get the wrong answer? Dorothy was about ten or eleven years old when she came to Oz to live, and had attended school in Kansas prior to that, so you'd think she'd know basic arithmetic. Perhaps it was just a moment of absent-mindedness, but what narrative purpose would that have served?
Thompson's even larger snub to mathematics, and especially with school math classes, occurs in Kabumpo, when the Elegant Elephant and Prince Pompadore stumble upon the city of Rith Metic. Here, the people all have numerals for heads, and while the text refers to them as "thin, spry little people," Neill simply draws them as numerals with faces and legs. In his defense, it's a little hard to imagine what Thompson was thinking of when she described the Figure Heads. They live inside giant arithmetic books with doors and windows, which remind Pompadore of "something disagreeable" even before he identifies them. The city is led by a wooden ruler who is "twice as large as a man"; I suppose his torso might be twelve feet instead of twelve inches long. The Ruler's assistant is Count It Up, a giant pencil who guides newcomers through the town. The rule is that anyone coming to Rith Metic has to work through numerous equations made up of the Figure Heads, and after finishing will be made into a word problem. The elephant and the prince escape with the help of the Curious Cottabus, who advises Pompa to turn a somersault. This functions as a sum assault, and drives the Figure Heads away. The very fact that a pun wins out against the math problems suggests to me that Thompson valued words over numbers.