Question

A man borrows Rs. 1000/- and agrees to repay the sum with a total interest of

Rs. 140/- in 10 installments. Each installment being less than the preceding
installment by Rs. 10/- . What should be the 1st installment?

Plzz answer in detailed steps.....
​

Answer 1

Rs 159

Explanation:

1000+140 = 1140

let first installment be a

second will be a-10, third will be a-20

hence we have

a+(a-10)+(a-20)+...........10 TERMS

CLEARLY THIS IS AN ARITHMETIC PROGRESSION

Sn = (n/2){2a+(n-1)d}

here Sn = 1140 n = 10 , d = a-10-a = -10

1140 = (10/2){2a +(10-1)(-10)}

1140= 5{2a+(9)(-10)}

1140= 5{2a-90}

5{2a-90} = 1140

2a-90 = 1140/5

2a-90 = 228

2a = 228+90

2a = 318

a = 318/2

a= 159