Jonah has collected 91 coins worth $7.20 in his piggy bank. his collection includes only dimes and nickels. how many dimes are there in jonah's piggy bank?

Gravel is being dumped from a conveyor belt at a rate of 25 ft3/min, and its coarseness is such that it forms a pile in the shape of a cone whose base diameter and height are always equal. how fast is the height of the pile increasing when the pile is 14 ft high? (round your answer to two decimal places.) ft/min