All members of our painting team paint at the same rate. If $10$ members can paint a $1000$ square foot wall in $10$ minutes, then how long would it take for $5$ members to paint a $1000$ square foot wall, in minutes?

Each member must paint 1000 / (10 * 10) = 1000 / 100 = 10sq ft per minute

So......5 members take

1000 / ( 5 * 10) = 1000 / 50 = 20 min

Another way to see this is that 5 members must take twice as long as 10 members !!!!