A forest covers 42,000 acres. A survey finds that 0.7 % of the forest is old-growth trees. How many acres of old-growth trees are there?

6,000,000

Explanation:

42,000 acres is the area you get after you multiply the number of acres of old-growth trees by 0.7%. So you would divide 42,000 by 0.7% to get the number of acres of old-growth trees.

# of acres of old-growth trees * 0.7% = 42,000

# of acres of old-growth trees = 42,000/0.7%

# of acres of old-growth trees = 6,000,000

PS. 0.7% = 0.007