Sure thing! We've got 40 and we're gonna multiply it by 10. That's the same as adding 40 to itself 10 times.
Step 1: 0 + 40 = 40
Step 2: 40 + 40 = 80
Step 3: 80 + 40 = 120
Step 4: 120 + 40 = 160
Step 5: 160 + 40 = 200
Step 6: 200 + 40 = 240
Step 7: 240 + 40 = 280
Step 8: 280 + 40 = 320
Step 9: 320 + 40 = 360
Step 10: 360 + 40 = 400

So, 40*10 = 400