60% of English words have a silent letter

Did you know that 60% of English words have a silent letter in them? Here are just 20 of them.
1. Debt (b)
2. Raspberry (p)
3. Castle (t)
4. Ghost (h)
5. Island (s)
6. Cupboard (p)
7. Thumb (b)
8. Wednesday (d)
9. White (h)
10. Answer (w)
11. Knee (k)
12. Knowledge (k) 13. Listen (t)
14. Half (l)
15. Whole (w)
16. Campaign (g)
17. Foreigner (g)
18. Yacht (c)
19. Autumn (n)
20. Writing (w)