Alright, let's work through 1780 times 646 step by step
1780 × 646 = 646 × (1780)
+ 646 × 0 that is equal 0
+ 646 × 80 that is equal 51680
+ 646 × 700 resulting in 452200
+ 646 × 1000 producing 646000

= 1149880
