There is no set speed because ice melts from the outside first. A solid block of ice, 1000g, will melt more slowly than 1000g of ice cubes, which will melt slower than 1000g of crushed ice. The more surface area exposed, the faster it melts. Also, it depends on the temperature of the ice. Ice from a -5C freezer will melt faster then ice from a -30C freezer.
You have asked this question twice. Why don't you carry out an experiment and find it our for yourself, using a kitchen scale, a timer, and a thermometer?