Question

no one has know how to solve this problem any know this

Answer 1

Answer:

1st installment = Rs 51

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Step-by-step explanation:

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

n = 40 Sn = 3600 a = 1st installment d = incremental in installments

3600 = (40/2)(2a + 39d)

180 = 2a + 39d    - Eq A

After 30 installment amount left = (1/3)*3600 = 1200

Amount paid in 30 installments =  3600-1200 = 2400

2400 = (30/2)(2a + 29d)

160 = 2a + 29d      - Eq B

Eq A - EqB

10d = 20

d = 2

using d = 2

160 = 2a + 58

a = 51

so 1st installment = Rs 51