Answer: 21/40
Step-by-step explanation:
I did the test
The greatest number of friends who can receive a necklace is 6. The reason why is because 6 is the greatest common factor of 72 and 42.
Each friend will have 12 blue beads and 7 red beads. If you divide 6 (GCF) with both numbers you get 12 and 7.
Hope this helps :3
