Quick way to find arbitrage

Anybody know how to quick calculate the arbitrage from foreign currency exchange rate problems:

1-problem with 3 rates and we can calculate the IMPLIED rate

2-problem with forward rate on the market and the implied expected spot rate calculated?

The curriculum presents in steps by steps, which I thought very time consuming. Any quick way is highly appreciated and will save us much time.Anybody know how to quick calculate the arbitrage from foreign currency exchange rate problems:

1-problem with 3 rates and we can calculate the IMPLIED rate

2-problem with forward rate on the market and the implied expected spot rate calculated?

The curriculum presents in steps by steps, which I thought very time consuming. Any quick way is highly appreciated and will save us much time.

Thanks