1. The contour interval is 20.
Explanation:
On the map we can see a relief that is depicted with contour lines. The contour lines tend to be very close to each other in general so we can safely make the assumption that the relief is relatively steep, though in accordance to the elevations it is not a high one, but instead the highest points are actually hills.
From the numeric markings on the contour lines we can see the numbers 100, 200, 300, and in between them there are four contour lines. Since the difference in elevation in between every fifth contour line is 100, if we divide that number by the number of contour lines from one thicker contour line to another, which is five, than we get a value of 20, meaning that that is the contour interval.
2. and 3. A has an elevation of 80, B of 60, W between 301 and 319, X between 21 and 39, and Y of 400.
Explanation:
The contour interval is 20 on this map, so with the values we already have as marked on every fifth contour line, as well as the additional contour elements on the map or better reading of it, we can relatively easily establish the value of any point. We have five points in question, some being on the contour lines themselves, while some inside of them, meaning that for the ones on the contour lines we can give an exact value, while for the one inside we can give approximate value.
The points A, B, and Y are all marked on contour lines. A is on the contour line just below the one marked with 100, so minus 20 means that it has a value of 80. The point B is on the second contour line below the one marked 100, so minus 40 means it has a value of 60. Point Y is marked on a main contour line which is not marked, but it is the first thick one after the one marked with 300, so 100 plus means it has an elevation of 400.
Points W and X are marked inside the contour lines, so we can just give a range of value for them. Point W is marked above the contour line marked with 300 and there is no next contour line. Since the contour interval is 20, it means that this point can have value ranging from 301 to 319. Point X is marked below the contour line with a value of 40 and there is no other contour line below, meaning that the value can be in the range of 21 to 39.
