A pipe can fill a cistern in 30 minutes and a waste-pipe can empty it in 1 hour. If both pipes are opened at once when the cistern is empty, how long will it take to fill the cistern?
plz plz solve it..I am confused

The final cost of a sale is determined by multiplying the price on the tag by 75%. which best describes the function that represents the situation?

Many newspapers carry a certain puzzle in which the reader must unscramble letters to form words. how many ways can the letters of emdangl be arranged? identify the correct unscrambling, then determine the probability of getting that result by randomly selecting one arrangement of the given letters.

Which set of lengths could represent the sides of a triangle? a. 3, 7, 10 b. 4, 5, 10 c. 6, 8, 14 d. 12, 6, 7