Question

the simple interest on Rs. 4000 for 4.25 yrs at 9%p.a is RS. 720 less than the simple interest on Rs. 6000 for 3.75 years at a certain rate of interest. find the rate
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Answer 1

Answer:

10 %

Explanation:

CASE 1 : P = 4000Rs. ; R = 9% ;

T = 4.25y = 4(1/4)y = (17/4)y

SO, C1's S.I. = (P×R×T)/100 =

\begin{gathered} \frac{ 4000rs \times 9 \times 17}{ 100 \times 4} \\ = 10rs \times 9 \times 17 \\ = 1530rs\end{gathered}

100×4

4000rs×9×17

=10rs×9×17

=1530rs

NOW, CASE 2 : P = 6000Rs. ; R = x ;

T = 3.75y = 3(3/4)y = (15/4)y

NOW, IT'S GIVEN THAT C1's S.I. IS 720 LESS THAN C2's S.I.

SO, C1's S.I. + 720Rs = C2's S.I.

=> C2's S.I. = 1530Rs + 720Rs = 2250Rs

SO,

C2's S.I. = (P×R×T)/100

\begin{gathered} = > 2250rs = \frac{ p \times r \times t}{100} \\ = > 2250rs \times 100 = 6000rs \times x \times \frac{15}{4} \\ = > x = \frac{ 2250rs \times 100 \times 4}{6000rs \times 15} \\ = > x = 10\%\end{gathered}

=>2250rs=

100

p×r×t

=>2250rs×100=6000rs×x×

4

15

=>x=

6000rs×15

2250rs×100×4

=>x=10%

THEREFORE, RATE = 10%