CIhalfyearly =P(1+r∕2)2−P SI=P×r×t Calculation: The compound interest for half-yearly compounding: r∕2=8∕2=4%=0.04 and Time, t=1 year (which is 2 half-year periods) CIhalfyearly =P(1+0.04)2−P ⇒P(1.04)2−P ⇒P(1.0816)−P ⇒P(1.0816−1)=P(0.0816) Calculate the simple interest: r=8%=0.08 and Time, t=1 year ⇒SI=P×0.08×1 ⇒SI=0.08P Now, CI - SI = Rs. 30 ⇒P(0.0816)−0.08P=30 ⇒P(0.0016)=30 ⇒P=30∕0.0016= Rs. 18750