Alright, let's work through 3407 times 6840 step by step
3407 × 6840 = 6840 × (3407)
+ 6840 × 7 what gives us 47880
+ 6840 × 00 yielding 0
+ 6840 × 400 that equals 2736000
+ 6840 × 3000 resulting in 20520000

= 23303880
