There was a group of 6 students who took a test. Another student joined the group after taking the test later. With her marks included the average score of the group went up by 3. This student has got ___ marks more than the average marks without her being included.
To go a distance of 40 km upstream a rower takes 8 hours while it takes her only 5 hours to row the same distance downstream. What was the rower's speed in still water?