Answer: Rs. 113.4

Explanation:
Simple Interest = PNR/100 = (840 × 3 × 9) / 100 × 2 = Rs. 113.4 

Answer: Rs. 5000

Explanation:
(CI – SI)for 2 years = P(R/100)2
50 = P(10/100)2 = P/100
P = Rs. 5000

Answer: Rs. 1132.08

Explanation:
A = P + SI T = 9 / 12 = 3 / 4 year
A = P + (PRT) / 100
A = P( 1 + RT / 100)
1200 = P [ 1 + (8 / 100 × 3 / 4)]
A = P (53/50) => P = (1200 × 50) / 53
P = Rs. 1132.08

Answer: Rs. 4.5

Explanation:
Total number of days:
March April May June July
(31 – 5) 30 31 30 29
Time (T) = 26 + 30 + 31 + 30 + 29 = 146 days = 146 / 365 years
= 2 / 5 years
I = PRT/100 = 300/100 × 15/4 × 2/5 = 9/2 = 4.5 years

Answer: Rs 223.75

Explanation:
Expenses = Rs 500
Repairs = 1.5(23000)/100 = Rs 345
Total expenses= Rs 845
Returns expected = 23000(8/100) = Rs 1840
Total rent per year = Rs (1840 + 845) = Rs 2685
Rent per month = 2685/12 = Rs 223.75

Answer: Rs 11200, Rs 9600, Rs 8400

Explanation:
Let A, B, C borrow Rs x, Rs y, Rs z respectively
x + y + z = 29200…(i)
A pays back Rs x + x(4)(5/100) = Rs 6x/5
B pays back Rs y + y(4)(10/100) = Rs 7y/5
C pays back Rs z + z(4)(15/100) = Rs 8z/5
6x/5 = 7y/5 = 8z/5
i.e. 6x = 7y =8z…(ii)
Solving (i) and (ii) simultaneously
X = 11200 , y= 9600 ,z=8400
A, B, C borrow Rs 11200, Rs 9600, Rs 8400 Respectively 

Answer: 11.7%

Explanation:
Let the sum invested be Rs x
Firm1:
x +x(8)(r/100) = 2x
r=12.5%
Firms2:
x +x(17)(r/100) = 3x
r=11.7%
the first firm pays better interest

Answer: 26 2/3%

Explanation:
Let the rate of interest per month be r
Total amount repaid = Rs 10, Interest = Re 1
(r/100)(9+8+7+6+5+4+3+2+1) = 1 =>r = 100/45
Rate of interest per annum = (100/45)12 = 26 2/3%

Answer: Rs 4000, Rs 2000

Explanation:
Let the two parts be P1 and P2
∴P1*2*6/100 =P2 *3*8/100
=> P1/P2=2/1
∴P1/2 =P2 /1 = 6000/3
∴P1 = Rs 4000 and P2 =Rs 2000

Answer: 20 years

Explanation:
Let the sum of money be Rs x and the rate of interest be r%
x + x(r)(10/100) = 2x
r = 10%
Let the period be n years
x + x(10)(n/100) = 3x
n = 20 years