If you analyse all the scale tone chords in the key of C major you come up with the following pattern:
This pattern remains the same regardless of the key. This means that if you look at the scale tone triads (three-note chords) in any major key, Chord 1 is always major, chord 2 is always minor, chord 3 is always minor, etc. The only thing that changes from one key to the next is the letter names of the chords. This can be demonstrated using at the scale tone triads for the key of G major.
By simply following the Roman numerals and remembering which chords are major, minor, etc, it is easy to transpose chords from one key to another. Here is the progression from Example 146 transposed to the key of G.