A few days ago, we discussed the \$100 million cost of converting gas station pumps to unit prices of more than \$1 a gallon. A reader suggested that the expenditure might be avoided by settling the unit price at one-tenth of the actual price per gallon, then multiplying the "total sale" number 10.

I said I was afraid of that proposal. Too many customers and attendants would need pencil and paper to do the arithmetic.

Many readers responded in disbelief. It seemed incredible to them that some people can't multiply by 10 in their heads. But I give them solemn assurance that millions of Americans cannot do that.

A few days ago I was in a store's checkout line. The woman ahead of me had filled her shopping cart with paper plates. "Church supper," she explained, not that anybody had asked.

The packages of plates were 95 cents each. Instead of counting 10 packages and ringing up \$9.50, the clerk pushed one stack along the counter and rang 95 cents. Then she pushed another package along and rang 95 cents again. And again. And again. Everything was done with elaborate care, and at a snail's pace.

In the midst of the process, the customer suddenly said, "Hold it. Don't ring up more than \$10 worth."

The register fell silent. Nothing moved. The clerk appeared to have been turned into stone. Finally she asked, "What's the matter?"

"I have only \$10," the customer explained. "That's all I can pay for. Will this number of plates come to more then \$10?"

Even the world's second-greatest grandchild could have responded at once, "If each package is 95 cents plus 5 cents tax, that's \$1 each, or ten for \$10. Actually, you'd get a couple of pennies change because 10 times 95 is \$9.50, so the tax would be something less than 50 cents, because 50 cents is the tax on a full \$10. Yes, lady, you have enough money."

Unfortunately, neither the checkout clerk nor the customer was that good at higher mathematics. They both got out ball point pens and proceeded to cover both ends of a paper bag with calculations. After a while, an assistant manager came over to find out why the checkout line was so long, and he also took out his ball point and added to the confusion.

Our gas lines move slowly enough as it is, and I would prefer not to make their pace subject to the mathematical skills of either vendors or consumers. Neither group is noted for its ability to work arithmetic problems with lightening speed.

Another example: A reader suggests we could help alleviate the gas crisis by banning the use of pleasure boats and pleasure aircraft. He says this would save 16 million gallons of gas.

I will concede that this sounds like an ocean of gasoline. However, if 16 million gallons were apportioned among 100 million vehicles, each motorist's share would be less than one-sixth of a gallon -- about five fluid ounces, or half a glass of beer. That wouldn't help much. If the gas shortage persists, we may have to curtail all pleasure driving, in automobiles as well as in boats and planes, but that will involve a great deal more than 16 million gallons.

A final word about avoiding the need to alter present gasoline pumps. Col. A.D. Robbins of Arlington was the first to inform me [and subsequently] that Canadian stations have for some time been setting their per-gallon price at half the true figure and have posted signs warning the public of this. People are aware that the "total sale" number must be doubled. I am assured that the system works, and perhaps it does. But I wish I could have the amount of money that will be involved in unnoticed mistakes. I'd be a rich man.

POSTSCRIPT

Syd Kasper asks, "Would you believe gas at 70 cents a gallon, no lines, and with every fill-up you get carwash coupons?"

Where? In the Windsor, just across the border from Detroit.

If you're wondering why the Canadians have begun to reset their gas pumps if their gas is only 70 cents, be advised I wondered, too. Syd says prices vary, and reminds us that Canadians use "imperial gallons," which are considerably larger and cost proportionately more. Syd did the arithmetic for us; his 70 cents refers to the equivalent price for American gallons.

PERSONAL NOTE

J.M.: I think your second letter chides me for not printing an accurate text of your letter, but I can't be sure because I can't decipher the second one any better than I did the first one. Try me again. Maybe with practice my reading will get better.

AIN'T IT THE TRUTH?

Paul Sweeney says, "We seem to be headed for a \$3 shrimp cocktail that contains one shrimp."