Tips & Tricks Short trick∶ We know that, Sum = Difference of CI and SI × (100/r)2 ⇒ Sum = 40 × (100/8)2 ⇒ Sum = Rs. 6250 Detailed solution∶ We know the formula for compound interest - ⇒ CI = [P { (1 +
r
100
)t − 1}] Where, CI = Compound interest P = Principal R = Rate of interest T = Time period Let the principal be P CI = P (1 + 8/100)2-P = 104P/625 SI = P × 8 × 2/100 = 4P/25 CI - SI = 40 104P/625 - 4P/25 = 40 P = 40 × 625/4 = Rs. 6250