Question

The simple interest on certain sum with the rate of interest being 7% pa 10% pa and 12% pa for first year 2nd year and 3rd years respectively is 8178 the sum is

Answer 1

Answer:

12980.95

Step-by-step explanation:

Let the sum be x

Then,(x×7/100)+(x×2×10/100)+(x×3×12/100)=8178

Or,7x/100+x/5+9x/25=8178

Or,7x+20x+36x/100=8178

Or,63x/100=8178

Or,x=8178×100/63=Rs.12980.95

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Answer 2

The sum is ₹ 28200.

Step-by-step explanation:

Let the sum be ₹ P.

The formula to be used is Simple Interest,  $SI =\frac{PRT}{100}$

For the first year, R = 7% and T = 1 year

Let the simple interest be represented by $SI_1$.

Then, $SI_1 =\frac{P\times 7 \times1}{100}$

Similarly for the second year, $SI_2 =\frac{P\times 10 \times1}{100}$ and the third year, $SI_3 =\frac{P\times 12 \times1}{100}$.

It is given that the sum of interests is  ₹ 8178.

It means,  $SI_1 + SI_2 + SI_3 = 8178$

or,

$\frac{P\times 7 \times1}{100} + \frac{P\times 10 \times1}{100} + \frac{P\times 13 \times1}{100} = 8178$

or,

$7P + 10P + 12P = 8178\times 100$

or,

$29 P = 817800$

or,

$P =\frac{817800}{29}$ = 28200 ₹.

Hence the principal sum is  ₹28200.