A certain sum is invested at simple interest at 15% p.a. for two years instead of investing at 12% p.a. for the same time period. Therefore the interest received is more by Rs. 420. Find the sum? Choose the correct choice:  A) s. 5000  B) s. 7000  C) s. 14000  D) s. 17000  E) s. 27000
Let the sum be Rs. x.   (x * 15 * 2)/100 - (x * 12 * 2)/100 = 420   =&gt; 30x/100 - 24x/100 =420   =&gt; 6x/100 = 420   =&gt; x = 7000.   ANSWER:s. 7000
<result>B</result>
A certain sum is invested at simple interest at 15% p.a. for two years instead of investing at 12% p.a. for the same time period. Therefore the interest received is more by Rs. 420. Find the sum?