Question

Kavita has a cumulative time deposit account in a bank. She deposits ₹800 per month and gets ₹16700 as maturity value. If the rate of interest is 5%p.a. find the total time for which the account is held.​

Answer 1

Answer in the attachment

Answer 2

Answer:

20 Months

Step-by-step explanation:

Let time be x months

Qualifying amount

= 800x(x+1)/2 = 400x(x+1)

SI = 400x(x+1)*5*1/1200

= (1/3)x(x+1)*5

= (5/3)x(x+1)

Principal = 800x

Hence,

800x + (5/3)x(x+1) = 16700

2400x + 5x^2 + 5x = 16700*3

x^2 + 481x - 10020 = 0

x^2 + 501x - 20x - 10020 = 0

x(x + 501) - 20(x + 501)

(x - 20)(x + 501)

x = 20, - 501

Negative value not possible

Therefore, time for which account is held = 20 months

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