Simple Interest-10th grade-6

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Mr. Tan kept $400 for 4 years and $500 for 5 years. The simple interest on
both of these together came to $196. The rate of interest per annum on
$400 was 1 ½ times of the rate of interest per annum on $500.
Find the two rates of interest.

Solution: Let the rate of interest per annum on $500 be r %

So, the rate of interest per annum on $400 is (3/2 * r) %

By the condition, (500 * r/100 * 5) + {400 * 3r/(2*100) * 4} = 196

=> 25r + 24r = 196

=> 49r = 196

=> r = 196/49

=> r = 4

So, the rate of interest per annum on $500 = 4% and the
rate of interest per annum on $400 = (3/2 * 4) % = 6 %