a ratio between two numbers is 5 : 4 and their l . c . m . is 80 . the first number is
"sol . let the required numbers be 5 x and 4 x . then , their l . c . m . is 20 x . ∴ 20 x = 80 ⇔ x = 4 . hence , the first number is 20 . answer c"
multiply(divide(80, multiply(5, 4)), 5)