If the contour intervals doubled how many contour lines are needed to show same elevation?

If the contour intervals doubled, you would need half as many contour lines to represent the same elevation range. For example, if originally the contour interval was 10 meters, and it is increased to 20 meters, each contour line would now represent a larger elevation change. Therefore, to depict the same range of elevation, the total number of contour lines required would be reduced by half.