Aptitude - Simple Interest - Discussion

Simple interest formula.

S.I=(PxRxT)/100 ---------------> (1)
where s.i =simple interest
R=rate %
P=sum or principal
T=year.


Amount = principal + simple interest
A = P + S.I ------------> (2).

From the question.
S.I = 81
Amount =450
R=4,5% P=?
A = P + S.I -----> (2)
450 = P + 81
p=450 - 81 =369 i.e :- P =369

And now using eq(1)


S.I =(P x R xT) / 100.............(1)
81=(369 x 4.5 x T) / 100
T= (81 x 100)/369 x 4.5
T= 4 years.

@Khusi.

Amount, the principal is the money which we lend for example I want to take 50 rupees from the bank so that will be loan or pricipal after 1 year the bank also want s s profit so they give a rate of interest for eg 2 pc so simple interest is prt/100 which will be 1 so at the end of the year they will have to give bank 501 rupees which is the amount.

So a=si + p.

t=(100*81)/(450*4.5)
t=(2*9)/4.5
t=18/4.5
y=1800/450=4 years.

So, lets dived them as 1800/450 = 4 years.

Bcoz if you want to convert decimal into number just put that much zeros same as above number here in 4.5 we convert it into 450 so just put two zeros above also bcoz from fraction point we increase 2 no. so 2 zeros are der.

Best of luck

First, find the how much per cent 81 of 450.
(81/450)*100 = 18%.

After finding 18% then simply divide the 18% with 4.5 interest
(180/45)*100 = 4years.

In simple words, we found that 81 is the 18% of 450.
So by using 4.5 % interest p.a we need to reach 18% by 4.5 + 4.5 + 4.5 + 4.5 = 4 years.

Yes @Sandhya I agree your view.

But here sum (or) principle is not given but he say that Rs450 to yield means we have to keep in mind that the amount never yield (produce) interest only the principle will (produce) interest; so the given amount is principle only.

I should explain clearly in this.

Then time =100 * 81/450 * 4.5,
= 2 * 9/4.5,
= 18/4.5,
= 18 * 10/45,
= 18 * 2/9,
= 2 * 2,
= 4 years.

They gave a number of Rs 450 so as per the formula amt = principal + interest, the amount should be subtracted from interest to get the principal but they directly takes principal as 450. Is it correct? Can anyone please clarify.

p = 450,r = 4.5,i = 81,t = ?
I = P * R * T/100 now we have to find t=? so,
t = 100 * I/P * R.
t = 100 * 81/450 * 4.5.
= 100 * 81/45 * 10 * 4.5 (45 * 10 = 450).
= 100 * 81/45 * 45 (4.5*10 = 45).
= 36/9.
t =4.

We can check by options also;

We know that S.I=PTR/100.
A.(450*3.5*4.5) ÷ 100=70.8,
B.(450*4*4.5) ÷ 100=81(ans) means 4years,
C.(450*4.5*4.5) ÷ 100=91.1
D.(450*5*4.5)÷100=1001.2.

Formula: SI = P * T * R/100,
SI = simple interest(81),
P = principal(450),
T = time(?),
R = rate(4.5),
T = SI * 100/P * R.
T = 81 * 100/450 * 4.5,
T = 8100/2025.
T = 4. Here s the answer.