Alright, let's work through 8145 times 1242 step by step
8145 × 1242 = 1242 × (8145)
+ 1242 × 5 resulting in 6210
+ 1242 × 40 that is equal 49680
+ 1242 × 100 that results in 124200
+ 1242 × 8000 that equals 9936000

= 10116090
