How long does it take light to get from the Sun to the Earth?
t = d/v = 1.5x1011 m / 3.0x108 m/s
Divide the mantissas (the numbers before the ‘x’)
0.5 x 1011 / 108 m / (m/s)
Subtract the exponents (the numbers above the 10)
Shift the decimal to the first place by adding or subtracting from the exponent.
Round to the minimum number of significant digits in the original numbers.
Cancel units to get the correct units
5.0 x 102 s = 500 s = 8.3 minutes