Question

Of 100 clock radios with digital tuners and / or CD players sold recently in a department store, 70 had digital; tuners and 90 and CD players. How many radios had both digital tuners and CD players?

Answer 1

60 of them have both digi tuners and cd players. Here's the logic: Since 90 definitively have cd players then 10 of them have only digital tuners(from the and/or clause). Since 70 definitively have digital tuners and 10 of them have only digital tuners (from above), 60 have both digi tuners and cd players. Ta Da....