All members of our painting team paint at the same rate. If $20$ members can paint a $4800$ square foot wall in $36$ minutes, then how long would it take for $9$ members to paint a $4200$ square foot wall, in minutes?

It takes 70 minutes for 9 team members (painting 60 sq ft per minute) to paint a 4200 sq ft wall.

Step-by-step explanation:

According to the situation the calculation is shown below:-

=

= 240 sq ft each member of the team in 36 minutes

=

= 6.67 sq ft each member of the team within 1 minute

= 60 sq ft for every 9 team members in one minute

=

= 70 minutes (or 1 hour and 10 minutes)

Hence, the 70 minutes is taken for 9 team members