Aptitude - Simple Interest - Discussion

If certain principal amounts to A1 in T1 year and to A2 in T2 year ,then the sum is given by = A2 .T1--A1.T2
_____________
T2--T1
Now use the formula
= 854 * 3 -- 815 * 4
________________
4--3
= 2562--3260
____________
1
= 698.

@Gayathri.

Superb explanation, You are genius Thank you.

@Rahul.

How? Please explain your solution clearly.

Yeah, this is the very easy solution. But can you explain this method with some other examples?

Like 9 years SI is 657 and 5 years SI is 555 so then?

@Tanuja

Use Vikram's explanation as reference

In case you didn't understand still, just logically understand that the:

Resultant sum = Principal + (SI * No. of years).

In the case of your example which is 9 years SI is 657 and 5 years SI is 555 so:

P + 9SI = 657 -------------(1)
P + 5SI = 555 -------------(2)

Subtracting (1) with (2) you get:

4SI= 102,
SI = 102/4,
=> SI = 25.5.

Substituting SI in (1) equation you get:

P + 9 (25.5) = 657,
P = 657 - 9 (25.5),
=> P = 427.5.

Your explanation helped me a lot, Thanks @Gayathri.

@Gayathri.

Very good explanation, easily understand. Thanks.

Thanks for all the solution and explanation.

It is given in sum that SI of 3yrs is 815 so why we need to multiply 3 with 39 to get SI for 3 years?

Please tell me if we subtract 854- 815 we get principal+ s.I for 1 year. Then can we consider it only s.I for 1 year? Please explain me.