Transposition sometimes is required for trumpet players. It most often occurs while playing in an orchestral setting but can surface in other venues such as reading out of a Fake Book, transposing from a hymnal or working with bad singers.
To a younger player this can be a shock and for that reason I have included this study which uses a melody everyone should be familiar with and in a range most players will feel comfortable.
Remember to use your eyes first and if your melody goes astray, your ears will guide you.
Eyes first!
Ears second!
