(24 + 31 + 18) days = 73 days = 1/5 year .

P = Rs 3000 and R = 18 % p.a.

  S . I = 3000 * 18 * 1 5 100

Principle amount = Rs. 29000

Interest = Rs. 10440

Let rate of interest = r%

=> So, time = r years

According to the question,

10440 = 29000 x r x r/100

290 x r x r = 10440

r x r = 1044/29 = 36

r = 6

Hence, the rate of interest = 6% and time = 6 yrs.

2500 in 5th year and 3000 in 7th year
So in between 2 years Rs. 500 is increased => for a year 500/2 = 250
So, per year it is increasing Rs.250 then in 5 years => 250 x 5 = 1250
Hence, the initial amount must be 2500 - 1250 = Rs. 1250

S.I. for 3 years = Rs. (12005 - 9800) = Rs. 2205.

S.I. for 5 years = Rs. 2205 3 × 5= Rs.3675

Principle = Rs.(9800-3675) = Rs.6125

Hence, Rate =  100 × 3675 6125 × 5 =12%

Let the sum invested be Rs. P

Let the rate of interest be R% per annum

=> Interest earned for 5 years = (P x 5 x R/100) = PR/20

Now, given that the interest earned increased by Rs. 600 if the Rate increased to (R+2)%

=> SI = (P x 5 x (R+2))/100 = PR/20 + 10P/100

Hence,

PR/20 + 10P/100 = PR/20 + 600

=> P = 6000

Therefore, the sum invested is Rs. 6000

Let the principle amount be Rs. P

Interest rate = 12%

Total amount he paid after 5 years = Rs. 1280

ATQ, 

$$\begin{gathered} P + I = PTR 100 + P \\ 1280 = P TR 100 + 1 \\ 1280 = P 5 x 12 100 + 1 \\ 16 P 10 = 1280 \\ P = 80 x 10 = 800 \end{gathered}$$

Hence, the amount he borrowed = P = Rs. 800.

S.I. = Rs. (15500 - 12500) = Rs. 3000.

Rate =  100 * 3000 12500 * 4 % = 6%

We know that I = PTR/100
=> P = 20250/4.5 = 4500
Now, new Interest at 5% = 4500x1x5/100 = 225
Now the additional amount = 225 - 202.5 = Rs. 22.5

As the interest rate increases by 2%
=> (7000x3x2)/100 = 420
                                   9200
                                  --------
                                   9620

Let man invested Rs. A And, after two years amount invested = (A +