Aptitude - True Discount - Discussion

Discussion :: True Discount - General Questions (Q.No.11)

11. 

Rs. 20 is the true discount on Rs. 260 due after a certain time. What will be the true discount on the same sum due after half of the former time, the rate of interest being the same?

[A]. Rs. 10
[B]. Rs. 10.40
[C]. Rs. 15.20
[D]. Rs. 13

Answer: Option B

Explanation:

S.I. on Rs. (260 - 20) for a given time = Rs. 20.

S.I. on Rs. 240 for half the time = Rs. 10.

T.D. on Rs. 250 = Rs. 10.

T.D. on Rs. 260 = Rs. 10 x 260 = Rs. 10.40
250


Pooja said: (Jan 10, 2012)  
Please elaborate the explanation.

Kuldeep said: (Jan 20, 2012)  
Please explain this answer.

Shivam said: (Feb 29, 2012)  
Please explain how this method is wrong
Amount is 260
PW would be (260-20)=240
20=240xrxt/100
rt=100/12

if t=t/2

TD=240 x r x t/2 x r/100
TD=240 x 100/2400
TD=10

Shivam said: (Mar 1, 2012)  
How simple interest is different from True Value, it seems both are same.

Please give example of both.

Anshika said: (Feb 24, 2013)  
I am unable to understand such type of ques, SI & CI ques, I can solve but there occur many problems when I solve it, please tell me easy of understand such type of questions.

Thanks.

Lara said: (May 22, 2013)  
First we have to find the value of (R*T) using the formula for PRESENT WORTH.
AMT = PRESENT WORTH + TRUE DISCOUNT.

Then calculate the value for (T/2) i.e., (R*T)/2, using this value and the same amount calculate the new PRESENT WORTH.

Nagaraj said: (Sep 23, 2013)  
Case 1:

PW would be (260-20) = 240.

20 = 240xrxt.

rt = 1/12.

case 2:

Sum due = 260, let's take true discount be 'X'.

PW = 260-X.

t = t/2 => rt = 1/24.

X = (260-X) x 1/24

25X = 260

X = 10.4.

T.D = 10.4.

Harini said: (Dec 7, 2013)  
How S.I and true discount equal?

Aparna said: (Jul 8, 2015)  
ptr/100 = SI.

240*tr = 2000.

Then tr = 2000/240.

Then how did you got that 1/12?

Please tell me.

Shivangi said: (Jul 14, 2015)  
What is SI?

Puzeetha said: (Oct 15, 2015)  
Please explain in detail.

Matlub Sheikh said: (Dec 18, 2015)  
What is SI? Please any one can explain?

Poonam Yadav said: (Apr 15, 2016)  
I am unable to understand these type of questions. Can anyone please explain more?

Somesh Saurabh said: (Jun 17, 2016)  
It's very simple.

This kind of situations when we take credit from some bank.

For e.g., let's say I have taken an amount of X i.e. Present Worth(P.W.).

Now I have promised to bank that I am going to pay the amount in T years. So they will tell directly about the total amount I need to pay after T years and this is Total Amount. The Same situation also comes when we sell something to someone who is not able to pay now and instead ask him to pay the amount after some time but at some interest.

For eg. I am to sell my watch at Rs. 1000 to you and you don't have money now to pay so I will tell you to pay rs 1500 after 2 years. It means that PW is 1000 and True Discount is 500.

The rate of interest (R) can be calculated by using simple formula TD = PW * T * R.

P.S. Please go by basics only. Don't use the formulae blindly.

Thank You.

Somesh Saurabh said: (Jun 17, 2016)  
Guys, there is only a little difference between SI and True Discount(TD).
SI is always calculated on the principal amount while TD is always calculated on the PW.

For eg., If the amount g is given as 1000 the SI will be SI = 1000 * R * T.
But for TD, first we need to get PW = (1000 - TD).
Then, TD = (1000 - TD) * R * T.

Hope you guys find it helpful. Thank You.

Deepesh Samant said: (Aug 16, 2016)  
As we know rt = 1/12.
Rt/2 = 1/24.

T.d = amount * rt / 100 + rt.
= 260 * 1/24 / 100 + 1/24.
= 10.4.

Wasim Ajaz said: (Aug 12, 2018)  
Here's the correct way,
Td=20,A=260,pw=240,
Td=pw * rt ÷ 100; rt=100/12.

ATQ, time is reduced to half so new time(rt2) will b 100/24.
Td=a * rt2/100+rt2;
Td=(260 * (100/24))÷ (100+100/24) = 10.4.

Vaishali Jagtap said: (Oct 10, 2018)  
I am not getting it. Please help it with the correct explanation.

Manish Kumar said: (Mar 23, 2019)  
@Somesh Saurabh,
Your explanation really helped us, but could anyone correct me if im wrong:
that is why divide by 100 is Missing:
i.e, SI = P*R*T/100.
so, SI on TD = (Amount - TD *R*T)/100.

Shawn Soares said: (Jul 19, 2020)  
How are you all calculate RT to be 1/12, by using TD=PW*(RT)?

Shouldn't the formula be TD=PW*(RT)/100? Which should give RT=100/12?

Pavan G J said: (Aug 21, 2020)  
It is correct, just take rt/100 = 1/24.

Smitha said: (Jun 15, 2021)  
T.D = 20
Amount = 260
P.w = Amount - TD = 240.
S.I on p.w = 20.

By formula:
R * T = S.I * 100/p.w = 25/3.

Again by question:
Td = p.w * R * T/100.

Where the Time is half so R*T/2.
i.e 25/6.
We get TD = 10.49.

Abi said: (Jun 19, 2021)  
@Smitha.

I am getting 10 as answer.

Post your comments here:

Name *:

Email   : (optional)

» Your comments will be displayed only after manual approval.