Question

Q1. The Simple Interest On Rs.4,000 For 4.25 Years At 9% P.A. Is Rs.720 Less Than The Simple Interest On Rs.6,000 For 3.75 Years At A Certain Rate Of Interest. Find The Rate.

Answer 1

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 =
$\frac{ 4000rs \times 9 \times 17}{ 100 \times 4} \\ = 10rs \times 9 \times 17 \\ = 1530rs$
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
$= > 2250rs = \frac{ p \times r \times t}{100} \\ = > 2250rs \times 100 = 6000rs \times x \times \frac{15}{4} \\ = > x = \frac{ 2250rs \times 100 \times 4}{6000rs \times 15} \\ = > x = 10\%$
THEREFORE, RATE = 10%

THERE YOU GO!!!......