You can do 90 sit-ups in 2 minutes your friend can do 135 sit-ups in 3 minutes do these rates form a proportion ? explain

Yes these rates to form a proportion. This is because if I am able to do 90 sit-ups in 2 minutes then the unit rate (amount of sit ups per minute) is 45. Since my friend does 135 sit-ups in 3 minutes then the unit rate is also 45. Both me and my friend do 45 sit-ups per minute.