Answer:
5
Explanation:
There are 3 feet in a yard, so 420 feet is 420/3 = 140 yards.
The total number of yards Edith needs is ...
65 yd + 580 yd = 645 yd
So, the total number of balls of yarn Edith needs is ...
(645 yd)/(140 yd/ball) ≈ 4.61 balls
Edith needs to buy 5 balls of yarn to make her projects.