I derive an annual income of Rs 688.25 from Rs 10000 invested partly at 8% per annum and partly at 5% per annum simple interest. How much of my money is invested at 5%?

Answer: A Let the money invested at 5% be x Then, (x*1*5)/100 + [(10000-x)*1*8]/100 = 688.25 => 3x =11175 => x= 3725.

Q. No. 2:

If the difference between the simple and the compound interests on the same principal amount at 20% for 3 year is Rs 48, then the principal amount must be

Answer: C Let the principal be
Rs 100. Then, S.I = (100*20*3)/100 = Rs 60 CI = 100(1 + 20/100)^{3} -100 = Rs 364/5 Thus, CI - SI = 364/5 - 60 = 64/5. If the difference is 64/5 , principal = Rs 100 If the difference is 48, principal = Rs 100*48/(64/5) = Rs 375

Q. No. 3:

If the difference between the simple interest and the compound interest compounded annually at the rate of 12% per annum on Rs 5000 for two years will be

Answer: D Difference between CI and SI is :- {5000(1 + 12/100)^{2} - 5000 } - {(5000*12*2)/100} => 5000((784-625)/625) - 1200 = Rs 72.

Q. No. 4:

Two equal sums of money were invested, one at 4% and the other at 9/2 %. At the end of 7 year, the simple interest received from the latter exceeded that received from the former by Rs 31.50. Each sum was

Answer: B Let the sum be Rs x Then, (x *9/2 *7)/100 - (x*4*7)/100 = 31.50 => 7x/100* 1/2 = 63/2 => x = Rs 900.

Q. No. 5:

Sanjay borrowed a certain sum from Anil at a certain rate simple interest for 2 year. He lent this sum to Ram at the same rate of interest compounded annually for the same period. At the end of two years, he received Rs 4200 as compounded interest but paid Rs 4000 only as simple interest, find the rate of interest.

Answer: D Let the money borrowed be x, rate = r%, time = 2 year 4000 = (x*r*2)/100 => rx =200000...........(i) Now, x(1 + r/100)^{2} = x+ 4200 => xr^{2}/10000 + 2xr/100 = 4200 ........(ii) From equation (i) and (ii) => 20r +4000 = 4200 => r = 10%

Q. No. 6:

P wants to secure an annual income of Rs 1500 by investing in 15% debentures of face value Rs 100 each and available for Rs 104 each. If the brokerage is 1%, then the sum of money he should invest is

Answer: C Let Rs x be the face value of debentures, then 15% of x =1500 => x* 15% =1500 => x = 10,000 Available value of debentures = (104/100 * 10,000) = Rs 10,400 Now brokerage = 1% of 10,400 = Rs 104 Sum of money invested = 10,400 + 104 = Rs 10,504.