Rs. 900 is lent at a certain rate of simple interest. After 9 months, another Rs. 600 is lent at a rate that is 1.5 times the original rate. If the total simple interest after 1 year is Rs. 72, find the original rate.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1i.e. 6.4%.
SI = (P × R × T)/100
Let the rate of interest = R%
₹900 at R% for 12 months or 1 year
SI = (900 × R × 1)/100 = 9R
₹600 at 1.5R% for last 3 months or 1/4 years
SI = [600 × 1.5R × (1/4)]/100 = 2.25R
Total SI = 9R + 2.25R = 11.25R
So, 11.25R = 72
⇒ R = 72/11.25 = 6.4%