yofxThe Unofficial Blog of the Tunxis Math Department

Here’s a coupon I just used at Valvoline for an oil change. There are two discounts either 10% off or $7. You are not supposed to be able to use both coupons on a service. This is an example of what is called an exclusive “or” in logic. You can have either/or but not both. The usual mathematical “or” is inclusive. More like the “or” in ‘cream or sugar’? Where the option is to have one, the other, or both. When we hear “or” used in speech, we usually rely on context to clear up which “or” we’re talking about. On math tests it is sometimes trickier. Be careful or be careful.