Aptitude - True Discount - Discussion

Discussion :: True Discount - General Questions (Q.No.5)

5. 

If Rs. 10 be allowed as true discount on a bill of Rs. 110 due at the end of a certain time, then the discount allowed on the same sum due at the end of double the time is:

[A]. Rs. 20
[B]. Rs. 21.81
[C]. Rs. 22
[D]. Rs. 18.33

Answer: Option D

Explanation:

S.I. on Rs. (110 - 10) for a certain time = Rs. 10.

S.I. on Rs. 100 for double the time = Rs. 20.

T.D. on Rs. 120 = Rs. (120 - 100) = Rs. 20.

T.D. on Rs. 110 = Rs. 20 x 110 = Rs. 18.33
120


Murali said: (Nov 23, 2010)  
Please provide some more explanation. Then it is easily understood by me and others.

Karthika said: (Dec 4, 2010)  
Please explain. I can't get the concept.

Revathy said: (Dec 27, 2010)  
Please help us out here.

Meha said: (Jan 5, 2011)  
Whar ever the formula is given at biginig that was not comparable here. Which formula you are used here? please expline the formula.

Karthick said: (Jan 5, 2011)  
Please explain the sum and which formula you are used here.

Raghubabu said: (Feb 5, 2011)  
I cant understand it please explain by another form.

Abhishek said: (Feb 23, 2011)  
According to question,
Amount=110,True Discount=10,Present Worth=110-10=100;
Now,we know,P.W.=(Amount*100)/100+(R*T);
So,100=(110*100)/100+(R*T);that implies (R*T)=10;
Again in question,
(R*2T)=(2RT)=2*10=20;Now,
P.W.=(110*100)/100+(2RT)=(110*100)/100+20=91.66;
So,T.D.=Amount-P.W.=110-91.66=Rs.18.34/- (clear)....

Shubha said: (Apr 15, 2011)  
How you have got p.W=(Amt*100)/(100+(r*t))

Vinay said: (Aug 28, 2011)  
The discount allowed on the same sum 110 is double the time means 10 becomes 20%

So, 20% will come.

Therefore, principal amount is 100 for both the cases

(20x 110)/120= Rs. 18.33

Anu said: (Oct 20, 2011)  
Thank you Abhishek.

Kuldeep Kumar Singh said: (Jan 20, 2012)  
@Abhishek thanks for explaation.

Dhana said: (Jan 24, 2012)  
Thanks abhishek.

Aejaz said: (Feb 26, 2012)  
This can be taken as principal as 100 and amount as 110 then from amount = p + PTR/100 then we get RT as 10 : Now 2RT =20
and Amount is 110 then find the principal from above formula we will get amount as 91.65 so the discount is 110-91.67=18.33

Madhukumar E said: (Nov 14, 2013)  
It's given that,

If, TD on 110 = 10 at certain time hence,
then, TD on 100 =20 at double the time hence,

110 = 20.
100 = ?

= 18.18.

In the same way.
If, TD on 120 = 20 at certain time hence,
then, TD on 110 = x.

120 = 20.
110 = ?

20/120 = 1/6.
1/6*110 = 18.33.

So 18.33 answer.

Kiruthi said: (Jun 15, 2015)  
Please explain without formula generaly.

Anvesh said: (Nov 26, 2015)  
Let suppose 110 should be paid after 1 year with a discount of Rs. 10.

-> Present worth (PW) = 110-10 = 100.

-> Rate = Discount*100/(PW*time) = 10.

The question is what will be the present worth, if the amount becomes 110 after 2 years with rate 10% per year.

-> Present worth = 110/(1+10*2/100) = 91.67.

-> Discount = 110-91.67 = 18.33.

Mamta said: (Dec 1, 2015)  
PW = Amt*100/100+rt = td*100/rt.

=> 11000/100+rt = 1000/rt.

=> rt = 10.

Now, we have amt 110 on t double at are % and need to find out new TD on new PW or you can say.

TD = Amt - PW.

= 110 - 110*100/100+r*2t.

= 110(1-100/100+2*10).

= 110(1-100/120) = 18.33.

Swati said: (Jan 11, 2016)  
What is the full form of S.I?

Balasubramanian said: (Apr 19, 2016)  
Good explanations for discount and time & work problem. It helps to understand easily.

Keerthi said: (Jul 18, 2017)  
Given.

T.D = 10, AMOUNT = 110.
SO, BY USING THE FORMULA.
100*AMT/(100+RT)=100 * T.D/(RT),
WE KNOW THAT RT= 10,

Since the question asked to find out the T.D after double the time
RT=20,
So, by using the same above formula T.D=18.3333.

Arvindkumargp said: (Aug 25, 2017)  
Thanks @Abhishek.

Devendra said: (Jun 18, 2018)  
Thank you for explaining the answer.

Swetha said: (Jun 27, 2018)  
Thank you @Abhishek.

Manisha said: (Jul 26, 2018)  
Thanks @Abhishek.

Jubair said: (Jan 16, 2019)  
Thanks @Abhishek.

Sudip Dhara said: (Apr 11, 2019)  
See, the true discount allowed is Rs. 10 and the amount to be paid after a certain time is Rs. 110.

We don't know the time and the present worth. So lets assume a value. Let's say the present worth is Rs.100, and the time is 1 year. Thus the Rate has to be 10%. Now double the time, so what is the present worth if Rs.110 was due in 2 years at 10%? It comes out to be Rs. 91.66. Thus the true discount becomes Rs.18.33.)

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