Aptitude - Compound Interest - Discussion

Very simple formula is;

p.(R/100)^2 = (compound interest - Simple interest) time duration 2 years.

@Gagan

SI = P * (n * r)/100.
CI = P((1 + r/100)^n - 1).

Now simplify both equations such that P comes to the left and rest to the right equate both to get r.

We can use the direct formula for this one.

The difference after 2 years = PR^2/100^2.

Here, P - Principal, R - Interest of Rate.

How we derive the shortcut trick for 2 or 3 years for the sum of money if the difference given b/w CI and SI? Anyone help me to clear these shortcut to improve myself. Please.

CI for 2 years - SI for 2 years = PR^2/100^2.
1 = P16/10000,
10000/16 = P,
P = 625.

Solution for CI on certain amount for 2 years is 2200 and 3 years is 3640. Find the rate?

Guys please help me.

Can anybody tell me the formula for finding rate and principle when compound interest and simple interest are given with time 2 years and SI = 800 and CI = 850?

(SI -CI) for 2 year = (r/100)^2 * principal.

Take as, C.I - S.I = Rs.1.

Then, for C.I ->use the Formula[x + y + {(xy)/100}].

For x&y ->put R% value( i.e.,) X=4 &y=4.

By this ,we get [4+4+{4*4/100}] = 8.15.
For S.I -> R * T = 4 * 2 = 8.
So , 8.15 - 8 = RS.1 => 0.16=1.

By this, 0.16% = 1 means,then 100%=?
So, cross multiply it
i.e., 100 * 1/0.16 = 625.

I am just trying to explain briefly, hence the sum looks like long . But you all just write the numerical step and look it .
It just takes few secs only try it.

SIMPLE STEP.

FORMULA :
Diff b/w SI and CI when T = 2yrs.

P = (D * 100^2)/R^2.
D =RS 1.
R = 4%.
SO, Answer is 625.


FOR DIFF B/W CI AND SI FOR 3 YRS
FORMULA

P = (D * 100^3)/R^2(300 + R).