Answer:
3780 bolts will be made by 8pm
Step-by-step explanation:
One Hour : 500 nuts or 840 bolts
Divide by 2
30 minutes : 250 nuts or 420 bolts
750 nuts : 500 + 250 = 750
so the machine took 1 hour and 30minutes
14:00 it started (2pm)
15:30 it switched to bolts
20:00 (8pm)
4 hours and 30minutes to get to 8pm
840 × 4 = 3360 bolts + 420 bolts = 3780 bolts was made