Alright, let's work through 1645 times 504 step by step
1645 × 504 = 504 × (1645)
+ 504 × 5 that equals 2520
+ 504 × 40 giving us 20160
+ 504 × 600 giving us 302400
+ 504 × 1000 which equals 504000

= 829080
