Alright, let's work through 3689 times 3490 step by step
3689 × 3490 = 3490 × (3689)
+ 3490 × 9 that is equal 31410
+ 3490 × 80 yielding 279200
+ 3490 × 600 that equals 2094000
+ 3490 × 3000 what gives us 10470000

= 12874610
