I'm afraid the other tutor's solution is incorrect. But we're just human, and all of us mess up sometimes. I've messed up a number of times! MAMMALIA The vowels are A,A,I, and A. The consonants are M,M,M, and L. There are only 5 basic ways we can arrange them, vowel and consonant-wise so that no vowels are put together: CVCVCVCV, VCVCVCVC, VCCVCVCV, VCVCCVCV, VCVCVCCV There are 4 vowels, among which 3 A's are indistinguishable. There are 4 consonants, among which 3 M's are indistinguishable. So for each of those 5 there are 4!/3!=4 distinguishable ways to place the 4 vowels. And there are 4!/3!=4 distinguishable ways to place the 4 consonants. So there are 5*4*4=80 ways to place them. Here are all 80, generated by a computer program in alphabetical order. It's fun trying to pronounce them. My favorite is Number 73, MAMALIMA. If your MAMA was a LIMA, you'd be a son of a bean. lol 1. ALAMAMIM 2. ALAMAMMI 3. ALAMIMAM 4. ALAMIMMA 5. ALAMMAMI 6. ALAMMIMA 7. ALIMAMAM 8. ALIMAMMA 9. ALIMMAMA 10. ALMAMAMI 11. ALMAMIMA 12. ALMIMAMA 13. AMALAMIM 14. AMALAMMI 15. AMALIMAM 16. AMALIMMA 17. AMALMAMI 18. AMALMIMA 19. AMAMALIM 20. AMAMALMI 21. AMAMAMIL 22. AMAMAMLI 23. AMAMILAM 24. AMAMILMA 25. AMAMIMAL 26. AMAMIMLA 27. AMAMLAMI 28. AMAMLIMA 29. AMAMMALI 30. AMAMMILA 31. AMILAMAM 32. AMILAMMA 33. AMILMAMA 34. AMIMALAM 35. AMIMALMA 36. AMIMAMAL 37. AMIMAMLA 38. AMIMLAMA 39. AMIMMALA 40. AMLAMAMI 41. AMLAMIMA 42. AMLIMAMA 43. AMMALAMI 44. AMMALIMA 45. AMMAMALI 46. AMMAMILA 47. AMMILAMA 48. AMMIMALA 49. ILAMAMAM 50. ILAMAMMA 51. ILAMMAMA 52. ILMAMAMA 53. IMALAMAM 54. IMALAMMA 55. IMALMAMA 56. IMAMALAM 57. IMAMALMA 58. IMAMAMAL 59. IMAMAMLA 60. IMAMLAMA 61. IMAMMALA 62. IMLAMAMA 63. IMMALAMA 64. IMMAMALA 65. LAMAMAMI 66. LAMAMIMA 67. LAMIMAMA 68. LIMAMAMA 69. MALAMAMI 70. MALAMIMA 71. MALIMAMA 72. MAMALAMI 73. MAMALIMA 74. MAMAMALI 75. MAMAMILA 76. MAMILAMA 77. MAMIMALA 78. MILAMAMA 79. MIMALAMA 80. MIMAMALA Edwin