If 7103 is divided by 25 then the remainder is
Since 7103=7(72)51=7(49)51=7(50−1)51
=7{5051−51C1 5050+51C25049−⋯−1}=7(5051−51C1 5050+51C2 5049−⋯)−7+18−18=7(5051−51C15050+51C25049−⋯)−25+18
= k + 18 (say)
∵ k is divisible by 25.
Hence remainder is 18.