Question

Raghu wish to buy a laptop. He can buy it by paying Rs 40,000 cash or by giving it in 10 installments as Rs 4800 in the first month, Rs 4750 in the second month, Rs 4700 in the third month and so on. If he pays the money in this fashion, find 

(i) total amount paid in 10 installments. 

(ii) how much extra amount that he has to pay than the cost?

Answer 1

4800 + 4750 + 4700 + … 10 terms 

Here a = 4800 

(i) d = t₂ – t₁ = 4750 – 4800 = -50 

n = 10 

S_n = (n/2) (2a + (n – 1)d) 

S₁₀ = (10/2) (2 x 4800 + 9 x -50) 

= 5 (9600 – 450) 

= 5 x 9150 = 45750 

Total amount paid in 10 installments = Rs 45750. 

(ii) The extra amount he pays in installments 

= Rs 45750 – Rs 40,000 

= Rs 5750