The fins attached to a surface are determined to have an effectiveness of 0.9. Do the rate of heat transfer from the surface decrease as a result of the addition of these fins?

The rate of heat transfer decreases.

Explanation:

Fin effectiveness is defined as the ratio of heat transfer rate from a  finned surface to the heat transfer rate from the same surface if there were no fins.  Its  value is expected to be greater than 1.

Having effectiveness  value of 0.9  which is less than 1 indicates that the heat transfer rate will decrease since a fin effectiveness smaller than 1 shows that the  fin acts as insulation (thermal insulation).

answer:

put more,