Aptitude - Compound Interest - Discussion

First i did for one year then converted into half:

CI = 1600*5/100 = 80 for one year we want for 6 months then its = 40 for next half year.

CI = 1640+1600*5/100 = 164 one year but we want for 6 months then its = 81.

Total interest is 40+81 = 121.

I have taken this formula:

A = 1600(1+2.5/100)^2+1600(1+2.5/100).
= 1600(1+41/40)^2+1600(1+41/40).

= 1681+1640.
= 3321.

Therefore less principle amount of 1600*2 = 3200 to get interest earned.

3321-3200 = 121.

Why subtract 3200 from 3321?

Because 3200 is the total amount of one year which is principle.

I think it will be as correct answer for everyone, the first deposit amt is 1600, after six month total amt is 1640 (Including 5% of one year interest for six months). We should assign this as A-case.

Next July 1st day second deposit amt is 1600, It should be as B-case. The end of the year amt is 1640 (Including 5% of one year interest of six months). But A-case deposited at one year, So total Mature amt is 1681 (Including 5% of one year interest of twelve months. Interest of Rs. 40 is Rs-1, So amt Rs-40 became as Rs-41).

Finally A-case + B-case are 1681 + 1640 = 3321. Deposit amt is Rs-3200 and Interest amt is Rs-121.

I am not able to understand the problem in these quick steps. Can anyone please help me understand in detailed process.

Guys most of you might be confused with the formula, lets do this way:

1st 6 months deposit = 1600,

Interest earned at 5% upto July = (1600 x 5/100 x 1/2) = 40.

Note: In compound interest interest gets added to the principle.

So P = 1640 now, and next deposit in July = 1600.

Total deposit = (1640+1600), interest = (3240 x 5/100 x 1/2) = 81.

Total profit earned as interest = 40+81 = 121.

Hope this helps.

Your answer are so useful guys. Keep it up.

Such a brilliant answers I got here. How you people can make this possible?

Please give some suggestion to improve my aptitude problem solving ability.

Is there any other way to solve this problem?