AMO 2019 Primary 6 (Grade 6) Question 6

A method squares numbers ending in 5: $25^2=625$ uses $2(2+1)=6$ followed by 25; $35^2=1225$ uses $3(3+1)=12$ followed by 25; $45^2=2025$ uses $4(4+1)=20$ followed by 25. If $245\times245=100N+25$, find $N$.