Group Set Swap, Tourney to Claris I've just bought a used road bike. after I arrived home I noticed one of the chain ring teeth was snapped.

I have a spare flat bar bike which I believe to be much newer than the one I bought.

Because of that and the snapped tooth I've had the idea of replacing the parts with parts from my old bike, rather than investing in a new chain ring.

Can you give me your thoughts please?

More images at
http://imgur.com/a/w5IZr
That chainring doesn't look particularly worn from this angle. The wear would make the teeth look less symmetrical and more like shark fins. That shorter tooth allows the chain to leave that ring more easily when you change gear.

Ensure the chain is not worn out using a gauge (see http://www.bikeradar.com/road/gear/article/bicycle-chain-wear-explained-46015/ for what types of gauge are available and how to use them). If you grab the chain at the front of the chainring and pull it away from the crank spindle, you shouldn't be able to get more than about 1mm of gap between the chain and the dips between the teeth.