Answer:
795
Explanation:
First, we find the circumference of 1 ring.
c = 2πr
c = 2 × 3.14159 × 8.4 mm
c = 52.7787 mm
The circumference of 1 ring is the length of spooled gold used for 1 ring.
The spool has a total length of 42 m.
42 m × 1000 mm / 1 m = 42,000 mm
The spool has a total length of 42,000 mm.
Now we divide the length of the spool by the length of 1 ring.
42,000 mm / 52.7787 mm = 795.78
He can make 795 rings.