Aptitude - Simple Interest - Discussion

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"Hold a true friend with both hands."

- (Proverb)

A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years. The sum is:

[A].	Rs. 650	[B].	Rs. 690
[C].	Rs. 698	[D].	Rs. 700

Answer: Option E

Explanation:

S.I. for 1 year = Rs. (854 - 815) = Rs. 39.

S.I. for 3 years = Rs.(39 x 3) = Rs. 117.

Principal = Rs. (815 - 117) = Rs. 698.

V.Malarvizhi said: (Tue, Jul 20, 2010 09:43:59 AM)

Why not applied principal formula si100/rt ?

Kannan said: (Thu, Nov 25, 2010 06:16:54 AM)

Why should not subsract with 854? Please clear my doubt....

Priya said: (Mon, Nov 29, 2010 10:04:37 AM)

@Lavanya and kanna To get 1 year difference we have to subtract 4year amount-3year amount this difference amount is the 1 year simple interest.. that's why.. Rs. (854 - 815) = Rs. 39 39 is 1year S.I. hope it helps you..

Nag said: (Tue, Feb 8, 2011 10:15:04 AM)

Thank you. This is explanation is very helpful for me.

Appu said: (Mon, Feb 21, 2011 08:29:22 PM)

Hai friends, Principle is the amount borrowed. Here, explain about SI of 3 years and 4 years. Assume P is the principal then, P+854 for 4 years and p+815 for 3yrs. So here it is necessary to find the SI of one year and subtract it from the 3 year or 4 year. That is, (815-117) = 698 and 854-156=698.

Vishnu said: (Tue, Mar 8, 2011 05:03:11 AM)

To get a si of one year or it might be two years if it is two year we have to divide it by two si=3yrs -2yrs willl give u one year si why should we have to go to risk.

Hari said: (Sat, Mar 26, 2011 03:14:01 AM)

I like this type of solutions thank you I think this answer also 1year 854-815=39 3years 39*4=156 854-156=698

Vijay said: (Fri, May 27, 2011 12:52:26 AM)

What is formula of simpe interest ?

Narasimha Reddy said: (Sat, Jun 4, 2011 07:01:21 AM)

S.I=PTR/100

Gayathri said: (Wed, Jun 22, 2011 01:15:27 AM)

Hi Friends! Principle = the amt u borrowed Interest = the small additional amt u pay for the amt u borrowed First let me explain u d question In the question, A sum of money at simple interest amounts to Rs. 815 in 3 years means the Principle amt together wit the interest paid for 3 yrs is Rs. 815 and similarly Principle amt together wit the interest paid for 4 yrs is Rs. 854 Therefore, if we subtract (854-815) we get the simple interest for 1 year as Rs. 39 Then, we calculate simple interest for 3 yrs as (39*3)= 117 Next step, we subtract (815 - 117) to get Principle amt for a yr as Rs. 698 Brief explanation for last step: 815 = Principle amt + int for 3 yrs ......equation 1 117 = int for 3 yrs ......equation 2 now subtract both equations, we get the principle amt I hope tat this explanation will be helpful to u

Reshmi said: (Wed, Jul 6, 2011 04:09:46 AM)

Thank you gayathri. You explained well.

Prathap said: (Wed, Jul 6, 2011 08:53:56 AM)

Simple and clear explanation by gayatri.

Raghu Karthic said: (Thu, Jul 28, 2011 06:47:37 PM)

Superb explanation gayathri. Thanks a lot.

Ashik said: (Sat, Jul 30, 2011 11:41:51 AM)

S.I for one yr=854-815=39 for 4 years=4*39=156 hence,854-156=698 i think it will be simple....

Vikram said: (Tue, Aug 2, 2011 10:37:50 PM)

According to the question, SI + P = 815 in three years and SI + P = 854 in four years so 815 - P = SI and 854 - P = SI Therefore, 815 - P = (P * 3 * R)/100 and ---- eq 1 854 - P = (P * 4 * R)/100 ---- eq 2 Now, eq 1 / eq 2 gives (815 - P)/(854 - P) = 3/4 Solving this eq, we get P = 698

Uma said: (Tue, Aug 16, 2011 09:40:22 PM)

@gayathri your explination is very helpfull. Thank you.

Harsh said: (Tue, Sep 13, 2011 08:29:52 PM)

I am not deciding which is easiest way to solve of the given question so please suggest me.

Venkatesh said: (Mon, Sep 19, 2011 12:35:32 PM)

Gayathri thank you so much before that I want to say myself I am dull even though I understood you are explantion it is very clear keep it up.

Jaya said: (Mon, Sep 26, 2011 08:45:43 PM)

Gayathri thanks a lot its vry clr & simple

Muskan said: (Sun, Nov 20, 2011 03:53:53 PM)

Please give me the solution of this question. A certain sum given on simple interest became double in 20 years. In how many years will it be 4 times.

Ranjitha said: (Tue, Dec 27, 2011 10:54:07 PM)

Its same friends.. you can do it in either way (39*4)=156 854-159=698 only

Sonia said: (Thu, Dec 29, 2011 08:12:49 PM)

Thanks Gayathri. Really your explanation is helpful.

Venkatesh Kumar said: (Tue, Jan 17, 2012 09:12:48 PM)

Thanks Gayathti for giving detailed explanation.