A sum of ₹ 1550 was lent partly at 5% and partly at 8% per annum simple interest. The total interest received after 4 yr was ₹ 400, The ratio of the money lent at 5% to that lent at 8% is

Let the sum lent at 5% = P
∴ Sum lent at 8% = (1550 - P)
Then, [(P x 5 x 4)/100] + [{(1550 - P) x 8 x 4}/100] = 400
⇒ 20P - 32P + 1550 x 32 = 40000
⇒ - 12P + 49600 = 40000
⇒ - 12P = - 9600
∴ p = ₹ 800
Sum lent at 8% = 1550 - 800 = ₹ 750
∴ Required ratio = 800 : 750 = 16 : 15