Aptitude - Simple Interest - Discussion

Each of the questions given below consists of a question followed by three statements. You have to study the question and the statements and decide which of the statement(s) is/are necessary to answer the question.

1. 

What is the principal sum?

I. 

The sum amounts to Rs. 690 in 3 years at S.I.

II. 

The sum amounts to Rs. 750 in 5 years at S.I.

 III. 

The rate of interest is 5% p.a.

[A]. I and III only
[B]. II and III only
[C]. I and II only
[D]. I and III only, or II and III only
[E]. Any two of the three

Answer: Option E

Explanation:

Clearly, any two of the three will give us the answer.

Correct answer is (E).


Moncy Kurien said: (Sep 27, 2010)  
We can find the principal amount by using the options I and II. But how can we find the principal amount using either I and III or II and III? Please explain.

Abcd said: (Jan 26, 2011)  
P + P.3.r% = 690---(1)

P + P.5.r% = 750---(2)

divide eqn 1 by 2 to get r and then p.

Udit Chauhan said: (Feb 4, 2011)  
Excellent abcd!!

Akshaya said: (Feb 11, 2011)  
Hi Abcd,

Using II & III

p+((p*5*5)/100)=750 .....(1)

Solving (1),we get p=600.

Similarly,we can do with I & III

Pooja said: (Aug 16, 2013)  
Please explain how p+(p*5*5/100) get?

Aman said: (Dec 3, 2013)  
According to third equation rate of interest is 5% so putting that in second equation that is p + p*rate*time/100 = sum.

p + p*5*5/100 = 750.

Chaud said: (Sep 4, 2014)  
P + P.3.r% = 690---(1).
P + P.5.r% = 750---(2).
Divide eqn 1 by 2 to get r and then p.

Please explain how to divide 1 by 2 to get r and then p?

Sam said: (Sep 27, 2014)  
Please explain how to get the answer from using only III?

Srira said: (Oct 6, 2014)  
Please explain the formula of this question and give me some easy way.

Anandhi D said: (Nov 6, 2014)  
I cannot understand Please explain the formula of this question and give me some easy way.

Dass said: (Dec 9, 2014)  
What is the basic formula for the sum?

9E Tej said: (Jan 10, 2015)  
Somebody please explain.

Manju said: (Jun 7, 2015)  
Help needed in understanding division of equations!

Ashis said: (Jun 21, 2015)  
In very simple level I explain to 9 how to get answer using ll & similarly only from (ll) we get P+S.I = 750 & T = 5.

And from (lll) we get R = 5.

Now P+(P*5*5)\100 = 750.

100P+25P = 750*100.
125P = 75000.
P = 600.

Qwers said: (Aug 1, 2015)  
There wasn't any information given with r% in the question (statements 1, 2). So I don't think taking are in both the cases is correct. So option D should be correct clarify.

Ashish said: (Aug 2, 2015)  
For those who need help regarding how to divide equation I and II (as suggested by abcd).

750 = P+(P*R*5)/100 => 75000 = 100P + 5PR. (i).

690 = P+(P*R*3)/100 => 69000 = 100P + 3PR. (ii).

Subtracting (i) & (ii) , we get.

R = 3000/P.

Now substitute it in any one either (i) or (ii) , we get.

P = 600.

Thanks.

Scientist said: (Aug 30, 2015)  
We can find answer using I and II as follows:.

5PR% = 750 - P.

3PR% = 690 - P --- Dividing them.
---------------.
5 750-P.

= 3 690-P.

3450 - 5P = 2250 - 3P.
1200 = 2P.
P = 600.

Using I and III.

I = PNR%.

Aman Kumar Shaw said: (Mar 8, 2016)  
How can we get the answer by using I and II. Please tell?

Aryan said: (Jun 29, 2016)  
I. Amount after 3 years = 690.
II. Amount after 5 years = 750.

Difference = SI for 2 years = 60.

SI for 1 year = 30,
SI for 3 years = 90,
SI for 5 years = 150,

Thus, Principal = 600.

Kishor said: (Jul 8, 2016)  
Please explain that how to get the answer from eq 1 & 2 only.

Vickma said: (Aug 11, 2016)  
AMOUNT = S. I + P.

690 - P = 3PR -> (1).
750 - P = 5PR -> (2).

Divide Eqn 2 by 1;

P = 600.

Use P = 600 in section I & III.

So, the correct option is 'E'.

T.Prabhu Pandiyan. said: (Aug 15, 2016)  
Anyone can please help me to understand the question.

Girish said: (Aug 26, 2016)  
690 - P = 3PR.
750 - p = 5PR.

Dividing both equations
(690 - P)/(750 - P) = 3/5.
-> (690 - P)5 = (750 - P)3.

By solving;

P = 600.

Shruthi said: (Aug 31, 2017)  
If it is any two of the 3 then there is a possibility of taking 1 and 2.

How can we get p using 1 and 2?

P V Snehil said: (Sep 11, 2017)  
We cannot get P using I and II, as we donot know the are when we have only these two statements.

Correct answer is D.

Mansi Arora said: (Dec 31, 2017)  
Hi @Aryan,

We are using here all the three given statements to get the value of P which is not given in the options.

Effoti said: (Mar 20, 2018)  
By using I and II;

S.I for 2 years = 750-690 = 60 as S.I is divided uniformly for each year, For 1 year = Rs. 30 and For 3 year = 90,
Principal = 690-90 = 600.

By using II and III
As Total Sum = Principal + Interest i.e 750 = P + I (after 5 years) ------> (1)
P = I *100 / R * T = I *100 / 5*5 = 4I,
Put value of P in eq. 1, 750 = 5I , I = 150 and P = 750 -150 = Rs. 600,

Similarly By using I and III.
P = I *100 / R*T = I*100/5*3 = 20/3(I),
690 = 20/3(I) + I , By solving this we get I = Rs.90 and P = 690 - 90 = Rs. 600.

Hence answer is E Any two of the three.

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