[tex]d = 4n -2 \\d + 2 = 4n\\\frac{1}{4}d + \frac{2}{4} = n\\\\n = 0.25d + 0.5[/tex]
For a 3-penny nail
[tex]n = 0.25d + 0.5\\ n = 0.25(3) + 0.5\\n = 0.75 +0.5\\\\n = 1.25[/tex]
For a 6-penny nail
[tex]n = 0.25d + 0.5\\n = 0.25(6) + 0.5\\n = 1.5 + 0.5\\\\n = 2[/tex]
For a 10-penny nail
[tex]n = 0.25d + 0.5\\n = 0.25(10) + 0.5\\n = 2.5 + 0.5\\\\n = 3[/tex]
Hope that helped :)
