1) The speed of light is 3 X 10^8 m/s. Express this speed in miles/hour . ( 1 mile = 1609 m)

my solving

3X10^8X3600/1609 = 67122 ( why this is wrong answer no as my book )

Itry by calculator I got 67122

2 ) Calculate the diameter of a 2.0 cm length of tungsten filament in a small lighbulb if its resistance is 0.050 ohms

I try to solve it

2 cm = 200 m

R= 0.050

r = root P X l over Pi X R

5.6 X 10^-8 X 2 X 10 ^ -2 over Pi X 0.05 = 4.220X10^-6

dimetr = 2r

= 2 ( 4.220X10^-6 ) 8.444016 X^-6