A man arranges to pay off a debt of 3600 euros by 40 annual instalments which form an arithmetic series.when 30 of the instalments are paid he dies leaving a third of the debt unpaid;find the value of first instalment.

Dear Abhishek

a + (a+d) + (a+2d)+......+(a+39d)  = 3600          (1)

(a+30d) +.....+ (a+39d) = 3600/3 = 1200            (2)

use ∑n = n(n+1)/2

solving we get

a=51, d=2

first instalment= 51 euro

All the best.

AKASH GOYAL

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