aptitude : : true discount
 
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Overview
Important Formulas
  Exercise
   Exercise 1
1.
The interest on a certain sum of money is Rs. 67.20 and the discount on the same sum of money for the same time and at the same rate is Rs. 60. What is the sum?
 
A.
Rs. 560

B.

Rs. 500
C.
Rs. 460
D.
Rs. 400
   
  Answer Discuss in Forum Calculator Workspace
Answer: A
Explanation :

Interest on Sum-T.D. = Interest on T.D.

=> Rs. 67.20-Rs.60 = Interest on Rs.60

=> Rs. 7(1/5) = Interest on Rs. 60

=> Rs. 1 = Interest on Rs.(60/7(1/5))

=> Rs. 67(1/5) = Interest on (60/7(1/5))*(67(1/5))

=> The required sum = ((60/7(1/5))*67(1/5))

                                      = Rs. 560







 
2.
A sum of Rs. 2550 is borrowed to be paid back in two years by two equal annual payments, 4% compound interst being allowed, what is the annual payment?
 
A.
Rs. 1352

B.

Rs. 135.20
C.
Rs. 1200
D.
Rs. 120
   
  Answer Discuss in Forum Calculator Workspace
Answer: A
Explanation :

Let x be the annual payment

The present value of the 1st payment

                        = Rs.(x/(1+(4/100)))

                        = (25x/26)

The present value of the 2nd payment 

                        = (x/(1+(4/100))2

                        = (625x/676)

Now, (25/26)x+(625/676)x = 2550

=> (1275/675)x = 2250

=> x = Rs. 1352

The annual payment = Rs. 1352







 
3.
What is the rate of interest when the P.W. of Rs. 8175 due in 5 months Rs. 8000?
 
A.
4%

B.

5%
C.
5(1/4)%
D.
5(1/2)%
   
  Answer Discuss in Forum Calculator Workspace
Answer: C
Explanation :

Present worth = Rs. 8000

Interest on Rs. 8000 for (5/12) year

                                     = Rs. 8175-Rs. 8000

                                     = Rs. 175

Interest on Rs. 100 for 1 year

                                     = Rs. (175/8000)*(100/5)*12

                                     = Rs. (21/4)

Rate = 5(1/4)% 







 
4.
If B.D. and T.D. on a certain sum for the same time and at the same rate be Rs. 172 and Rs. 160 respectively, find the sum.
 
A.
Rs. 229(1/3)

B.

Rs. 2290(1/3)
C.
Rs. 2293(1/3)
D.
Rs. 2293
   
  Answer Discuss in Forum Calculator Workspace
Answer: C
Explanation :
S.D. = ((B.D.*T.D.)/(B.D.-T.D.))
         = ((172*160)/(172-160))
         = Rs.((172*160)/12)
         = 6880/3
         = Rs. 2293(1/3)






 
5.
Find the true discount on a bill for Rs. 1270 due 7 months hence at 10% per annum.
 
A.
Rs. 10

B.

Rs. 35
C.
Rs. 70
D.
Rs. 170
   
  Answer Discuss in Forum Calculator Workspace
Answer: C
Explanation :
T.D. = ((A*R*T)/(100+RT))
        = ((1270*10*7)/(100+10*(7/12))12)
        = ((1270*10*7)/1270)
        = Rs. 70






 
6.
Find the persent worth of Rs. 264 due in 2 years hence at 5% per annum.
 
A.
Rs. 200

B.

Rs. 240
C.
Rs. 250
D.
Rs. 280
   
  Answer Discuss in Forum Calculator Workspace
Answer: B
Explanation :
P.W = ((100*A)/(100+RT))
        =  Rs.((100*264)/(100+5*2))
        =  Rs.((100*264)/110)
        =  Rs. 240






 

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