Question 824397
10+15+20+25 ...
a_n = 5 (n+1) (for all terms given)
12000 = 5 (n+1) (for all terms given)
n = 2399 days
Wednesday, April 17, 2013+2399 days
Monday, November 11, 2019
which is the 101 st anniversary of the end of WWI
2147 days from now xmas