To approximate the size of USA in relation to Ethiopia we proceed as follows:
Size of Ethiopia GDP in 2017=$ 76.9x10^9
Size of USA GDP=19.6x10^12
thus the scale factor of USA to Ethiopia will be:
19.6x10^12/76.9x10^9
=254.9
this can be written as a whole number to be
255
the economy of US is 255 times that of Ethipia