aptitude : : simple interest
 
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Overview
Important Formulas
  Exercise
   Exercise 2
   Exercise 1
1.
If a certain sum of money lent out at simple interest amounts toRs. 368 in 3 years and thereafter to Rs. 400 in another 2 years, the sum lent is:
 
A.
300

B.

320
C.
290
D.
325
   
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Answer: B
Explanation :
Amount  after 3 years = Rs. 368
Amount  after 3 + 2  = 5 years = Rs. 400
SI for 2 years = Rs. 400 - Rs. 368 = Rs. 32
SI for 1 year = 32/2 = 16
And SI for 3 years  = 16 x 3 = Rs. 48
Principal sum = Rs. 368 - Rs. 48 = Rs. 320 Therefore, the sum lent = Rs. 320
 
 






 
2.
The simple interest on a sum of money is Rs. 144. If rate per cent of the interest per annum equals the number of yearsthe rate per cent per annum is:
 
A.
10%

B.

12%
C.
15%
D.
8%
   
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Answer: B
Explanation :
Suppose  the  sum  of  money  = Rs.  100
And Rate= T%
Time = T years
so, 144=(100 x T xT)/100
T2 = 144 or T = 12
So, Rate of interest = 12%
 






 
3.
A borrowed Rs. 2500 at a certain rate of simple interest and Rs. 1500 at 3%  higher rate of interest. If after 4 years the interest paid by him in both cases is Rs. 1140, the former rate of interest was:
 
A.
5%

B.

6%
C.
8(1/2)%
D.
5(1/2)%
   
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Answer: B
Explanation :
Suppose the former rate p.a. = x%
:.In the first case,
P = Rs. 2500, R = x%, T = 4 years
SI = (2500 x X x 4)/100 = Rs.100x
In the second case,
P = Rs. 1500, R = (x + 3)%, T = 4 years
S.l. = (1500x(x+3) x 4)/100
= Rs. 60 (x + 3)
According to question,
Total interest  in both  cases = Rs.  1140 lOOx + 60(x + 3) = 1140
or, 100x + 60x + 180 =  1140
or,     160x = 1140 - 180
or,     160x = 960
 
or,     X = 960/160 = 6%
Former  rate of interest = 6% p.a.
 
 






 
4.
If a certain sum of money at simple interest amounts to Rs. 1900 in 3 years and to Rs. 2050 in 5 years, the rate per cent per annum is :
 
A.
4(1/2)%

B.

3(1/2)%
C.
2(1/2)%
D.
5(1/4)%
   
  Answer Discuss in Forum Calculator Workspace
Answer: A
Explanation :
Amount  after 3 years = Rs. 1900 
Amount after 5 years = Rs. 2050
Simple interest  for 2 years
= Rs. 2050 - Rs. 1900 = Rs. 150
. .  Simple interest for  1 year = 150/2 = Rs.75
Simple interest for 3 years
= Rs. 75 x 3 = Rs. 225
Principal = Amount after 3 years- S.I. for 3 years
= Rs. 1900 - Rs. 225 = Rs. 1675
Rate = (225 x 100)/(1675 x 3) = 4(1/2)%(approx)






 
5.
What annual instalment should be paid to clear the debt of Rs. 645 in 4 ye ars at the rate of 5% p.a. simple Interest?
 
A.
(a) Rs.160

B.

Rs .  185
C.
Rs.150
D.
Rs. 190
   
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Answer: C
Explanation :
Suppose each  instalment  =  Rs.  100
It is clear that if  the same amount of Rs.  100 is paid at the end of 2nd, 3rd and 4th years also then  the amount so settled will be Rs.  100 + Rs. 105 + Rs. 110
+ Rs.  115 = Rs. 430
Therefore, to clear the debt of Rs. 430 annual instalment
= Rs.  100
:.To  clear  the  debt  of  Rs.  645,  annual  instalment = (100 x 435)/645 = Rs.150
So, Annual instalment will be Rs.150






 
6.
A sum of Rs. 1850 lent out for 5 years at 3% p.a . simple interest will amount to :
 
A.
Rs. 2227 .75

B.

Rs . 2127.50
C.
Rs. 2137.50
D.
Rs. 2086.50
   
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Answer: B
Explanation :
Principal  = Rso  1850, Rate = 3%, Time = 5 years
SI = (1850 x 3 x 5)/100 = Rs.277.50
Amount = Principle + Simple Interest
=> Rs.1850+Rs.277.50
=> Rs.2127.50






 
7.
Sitaram invested an amount of 7450 at the rate 6% pe r annum rate of simple intrest. After h ow many years will he obtain the total amou nt of 879 1?
 
A.
5 yr

B.

3 yr
C.
2yr
D.
6yr
   
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Answer: B
Explanation :
(8791-7450) = (7450 x 6 x t)/100 
=> t= (1341 x 100)/(7450 x 6) = 3yr






 
8.
Mahesh invested an amount of 12050 at simple interest. He got an amount of 13496 at the end of 2 yr . At what rate of interest did he invest?
 
A.
12% per annum

B.

8% per annum
C.
6% per annum
D.
4.5% per annum
   
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Answer: C
Explanation :
Let the rate of interest be r% per annum.
=> 13496-12050 = (12050 x r x 2)/100 
=> r= (1446 x 100)/(12050 x 2) = 6% per annum






 
9.
The simple interest on a sum of Rs. 892 lent out at 6% p .a. for 8 months will be :
 
A.
Rs. 36.68

B.

Rs . 35.68
C.
Rs. 48.58
D.
Rs. 33.38
   
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Answer: B
Explanation :
P = Rs.892, R = 6% and time = 8months or 8/12 = 2/3 year
SI = (892 x 6 x 2/3)/100 = Rs.35.68
P = (SI x 100)/(R x T) = (81 x 100)/(6 x 4(1/2)) = (81 x 100 x 2)/(6 x 4) = Rs.300






 
10.
A sum of money amounts to Rs. 1150 in 3 year s and to Rs. 1250 in 5 years at a certain rate per cent p.a. simple interest. The rate per cent p.a.will be :
 
A.
5%

B.

8%
C.
7%
D.
6%
   
  Answer Discuss in Forum Calculator Workspace
Answer: A
Explanation :
Amount  after 3 years = Rs.  1150 Amount after 5 years = Rso  1250. 
Simple  interest  for  2  years = Rs. 1250- Rso 1150 = Rs. 100
Simple  interest  for  1  year = Rs. 100/2 = Rs. 50
Simple  interest  for  3  years = 50 x 3 = Rs. 150
Principle = amount after 3 years - interest of 3 years = 1150-150 = 1000Rs
Rate = (SI x 100)/(P x T) = (50 x 100)/(1000 x 1) = 5% 
 
 






 

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