49 points are marked on a sheet of paper in a square. Adjacent points horizontally or vertically are separated by exactly 1 centimetre.
How many straight lines of length 5 centimetres can be drawn between points in the design?
I have attempted to solve this problem taking into account the lines going through 6 points and the 5 cm diagonal lines with height 4 cm and width 3 cm. However, these approaches have been unsuccessful. The answer is 76 lines, but I cannot see how to reach this value. How is this problem solved and am I missing anything?