All members of our painting team paint at the same rate. If $50$ members can paint a $3600$ square foot wall in $20$ minutes, then how long would it take for $25$ members to paint a $4000$ square foot wall, in minutes?

Number of square ft painted in one minute = 3600 / 20 = 180

Number of square ft painted in one minute by one person = 180 / 50 = 3.6 sq ft

Then 25 people can paint 25 * 3.6 = 90sq ft in one minute

So....the number of minutes to paint a 4000 sq ft wall = 4000 / 90 ≈ 44.4 min