Question 1197721
<br><pre>
18/12 + 18/20 + 18/30 + ... + 18/1260

18(1/12 + 1/20 + 1/30 + ... + 1/1260)

18(1/(3*4) + 1/(4*5) + 1/(5*6) + ... + 1/(35*36)

18*{{{sum(1/(i(i+1)),3,35)}}}

18*{{{sum((1/i-1/(i+1)),3,35)}}}

18*((1/3-1/4) + (1/4-1/5) + (1/5-1/6) + ... + (1/34-1/35) + (1/35-1/36))

18(1/3-1/36) = 6-1/2 = 5.5</pre>

ANSWER: 5.5<br>