Question

What's the hight of a million pennies

Answer 1

The thickness of a brand new US penny that hasn't been
worn down is 1.52 millimeters.

If you have a million pennies, there are many ways to arrange them.
You can pile them all in one pile, or shovel them into many piles, or
stack them up in any number of stacks up to a half-million stacks
with two pennies in each stack, or try somehow to stack them all up
in one stack that's a million thicknesses high.

Any stack with 'n' pennies in the stack is  1.52n millimeters high.

If you somehow succeed in stacking all million of them in one stack,
then the height of that stack would be . . .

       (1,000,000) x (1.52 mm) =  1,520,000 millimeters
                                                         152,000 centimeters
                                                             1,520 meters
                                                               1.52 kilometers

                                            (about 59,842.5 inches
                                                          4,986.9 feet
                                                         1,662.3 yards
                                                               7.56 furlongs
                                                            0.944 mile
                                                                  all rounded)