How do i write 0.624 in expanded form?

)a smart phone has dimensions of 4.9 inches (height), 2.3 inches (width) and 8.0 millimeters (depth). what is the volume of the smart phone in cubic centimeters? (1 in = 2.54 cm)

Find the volume of the solid generated when the region bounded by y= x and y= 4√x is revolved about the x-axis the volume of the solid is: (type an exact answer cubic units)

Dylan and dusty plan to take weekly surfing lessons together. if the 2-hour lessons are $20 per person and they plan to spend $100 each on new surfboards, what is the maximum number of lessons the two can take if the total amount spent for lessons and surfboards is at most $480?