A series of book was published at seven years intervals when the seventh book was published the total sum of publication year was 13, 1524. first book was published in? Choose the most appropriate option:
A) 1911  B) 1912  C) 1913  D) 1914  E) 1915
First of all total sum of publication years is 13524 not 131524.   Let the first year is x.   so the years are x, x+7, x+14, x+21, x+28, x+35 and x+42.   Now Sum of all years = (n/2)(2a+(n-1)d) [n=number of years, a=first year, d=difference of two years]   =(7/2)(2x+(7-1)7)   =7x+147   1911gain Sum of all years = 13524   So, 7x+147=13524   =&gt; x=1911   1911NSWER:1911
<result>A</result>
A series of book was published at seven years intervals when the seventh book was published the total sum of publication year was 13, 1524. first book was published in?