When transposing chords, a similar system can be used. As you learnt in lesson 2, the chords C, F and G correspond to the first, fourth and fifth notes of the C major scale and so are known as chords 1, 4 and 5 in the key of C.
The chord numbers remain the same regardless of the chord type. E.g. The chord I shown above could be a C major, C minor or a C7. It will still be described as chord 1 as long as it is built on a C root note. To transpose these chords to the key of G, you would simply find the same chord types built on the first, fourth and fifth notes of the G major scale as shown below.
The following examples demonstrate a part played first in the key of C major and then in G major.
Here is the same part in the key of G. Notice that the left hand part has been raised in pitch, while the right hand part has been lowered. This type of alteration is common when transposing. The keyboard positions you choose depend on what sounds best in the particular key.
Here is another part in the key of G. Learn it from memory and then transpose it to the key of C.