How many 6-digit numbers can be formed using the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, if repetitions of digits are allowed?

To keep cylindrical tanks from tipping over, a designer is planning to enlarge the original area of the base by 50%. the new tank should have the same volume as the original. how should the designer change the height of the tank? a: make it 50% taller than the height of the original tank. b: make it 6623% taller than the height of the original tank c: make it 3313% shorter than the height of the original tank d: make it 50% shorter than the height of the original tank.