The students were shown either the entire picture or a picture with one of the three parts (a), (b) or (c) left out(upper, middle or lower part of Figure 1) in order to find out which parts are essential to find the answer. The students were allowed help such as a calculator, a textbook, a paper and a pencil.When they looked at these pictures, the students were asked if a cyclist needs more, less or the same time cycling with or without wind for a fixed distance and the return journey. This question had to be answeredanonymously and spontaneously within 2 min in each group. Since this question is about the time needed,finding the answer requires application of a reciprocal relation, since time for a constant movement is distances divided by speed v. When speed is increased and altered by wind speed vWIND = Δv, then the time t comesout to be: