Jim runs 50% faster then Bob. In a 1200m race how much of a head start should Bob get to make the race fairĀ 

I got a 600m head start but am I right??

No, a 600m head start would mean that Jim runs twice as fast as Bob.

Jim runs 3m while Bob runs 2m. So, when Jim has run 1200m, Bob has only run 800m.

So, give Bob a 400m head start.

Doesn't seem like Jim is getting a fair deal, though ...