The scale drawing of a deck that Mr. Food is building measures15cm by 21cm. Each 3cm on the scale drawing equals 5 feet.

What are the actual dimensions of the deck?

To find the actual dimensions of the deck, we need to use the scale ratio given.

First, calculate the scale ratio:
3cm on the scale drawing = 5 feet in reality
1cm on the scale drawing = 5/3 = 1.67 feet in reality

Next, find the actual dimensions of the deck:
Length: 21cm on the scale drawing
Actual length = 21cm x 1.67 feet/cm = 35.07 feet

Width: 15cm on the scale drawing
Actual width = 15cm x 1.67 feet/cm = 25.05 feet

Therefore, the actual dimensions of the deck that Mr. Food is building are 35.07 feet by 25.05 feet.