Calculate the number 399
NUMBERMANIA: Calculate the number 399 using numbers [4, 2, 7, 4, 22, 670] and basic arithmetic operations (+, -, *, /). Each of the numbers can be used only once.Correct answers: 2
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Gas MaskIn 1849, the forerunner of modern gas masks is patented by Lewis Phectic Haslett of Louisville, Ky. His "inhaler or lung protector" design used woolen fabric (or other porous material) to filter dust and other material from the air (U.S. No. 6,529). |