We're going to solve 1687 multiplied by 3989
1687 × 3989 = 3989 × (1687)
+ 3989 × 7 which equals 27923
+ 3989 × 80 which equals 319120
+ 3989 × 600 what gives us 2393400
+ 3989 × 1000 resulting in 3989000

= 6729443
