Just for information, 1 light-year is equivalent to the distance travelled by light in 1 year moving in a vacuum. 1 light-year is about 9.4607 * 10^{15} metres.

1 astronomical unit (AU) is equivalent to the average radius of the Earth's orbit. 1 AU is about 1.4960 * 10^{11} metres.

Simple arithmetic calculation yields the answer that 1 light-year = 63240 AU to a good approximation.
Answered by:
Ryan Leong, Undergraduate, NUS, Singapore

'Physicists like to think that all you have to do is say, these are the conditions, now what happens next?'