Piano key naming exercise focusing on accidentals and enharmonics.

Explanation:
We are given a piano keyboard diagram with white keys labeled C, D, E, F, G, A, B (in order), and black keys numbered 1–10. The task is to name each black key using accidentals: sharps (♯) or flats (♭), and then answer the conversion questions (11–20).

First, recall how black keys relate to white keys:
- Each black key is either a sharp (♯) of the white key *to its left, or a flat (♭) of the white key *to its right.
- On a piano, the black keys are in groups of 2 and 3. Between C–D–E there are two black keys (C♯/D♭ and D♯/E♭). Between F–G–A–B there are three black keys (F♯/G♭, G♯/A♭, A♯/B♭).

From the diagram:

Black keys 1–5 (with sharp names)
- Key 1 is between C and D → C♯
- Key 2 is between D and E → D♯
- Key 3 is between F and G → F♯
- Key 4 is between G and A → G♯
- Key 5 is between A and B → A♯

So:
1 = C♯, 2 = D♯, 3 = F♯, 4 = G♯, 5 = A♯

Black keys 6–10 (with flat names)
- Key 6 is between C and D → D♭
- Key 7 is between D and E → E♭
- Key 8 is between F and G → G♭
- Key 9 is between G and A → A♭
- Key 10 is between A and B → B♭

So:
6 = D♭, 7 = E♭, 8 = G♭, 9 = A♭, 10 = B♭

Now solve questions 11–20:

11. C♯ = ___♭
C♯ is the same note as D♭ (since C♯ and D♭ are enharmonic equivalents). So C♯ = D♭

12. E♭ = ___♯
E♭ is the same as D♯ (black key 2). So E♭ = D♯

13. A♭ = ___♯
A♭ is the same as G♯ (black key 4). So A♭ = G♯

14. D♯ = ___♭
D♯ = E♭ (black key 7). So D♯ = E♭

15. G♭ = ___♯
G♭ = F♯ (black key 3). So G♭ = F♯

16. B♭ = ___♯
B♭ is the same as A♯ (black key 5). So B♭ = A♯

17. F♯ = ___♭
F♯ = G♭ (black key 8). So F♯ = G♭

18. D♭ = ___♯
D♭ = C♯ (black key 1). So D♭ = C♯

19. G♯ = ___♭
G♯ = A♭ (black key 9). So G♯ = A♭

20. A♯ = ___♭
A♯ = B♭ (black key 10). So A♯ = B♭

Let’s double-check all:
- C♯ ↔ D♭ ✔
- D♯ ↔ E♭ ✔
- F♯ ↔ G♭ ✔
- G♯ ↔ A♭ ✔
- A♯ ↔ B♭ ✔

All match standard piano enharmonics.

Final Answer:
11. D
12. D
13. G
14. E
15. F
16. A
17. G
18. C
19. A
20. B