Question

Raghu wish to buy a laptop. He can buy it by paying ₹ 40,000 cash or by giving it in 10 installments as ₹ 4800 in the first month, ₹ 4750 in the second month, ₹ 4700 in the third month and so on. If he pays the money in this fashion, find how much extra amount that he has to pay than the cost?

Answer 1

4800 + 4750 + 4700 + … 10 terms

Here a = 4800

d = t₂ – t₁ = 4750 – 4800 = -50

n = 10

S_n = `"n"/2` (2a + (n – 1)d)

S₁₀ = `10/2` (2 × 4800 + 9 × -50)

= 5 (9600 – 450)

= 5 × 9150

= 45750

Total amount paid in 10 installments = ₹ 45750.

The extra amount paid = amount paid in 10 installment – cost of the laptop

= ₹ 45750 – ₹ 40,000

= ₹ 5750