Question

use the map to answer questions 1 - 9.
topographic map #1
1 multiple choice 5 points
what is the contour interval?
1000
125
500
100
2 multiple choice 5 points
what is the elevation at point a?
3400
3375
3600
3300
3 multiple choice 5 points
what is the elevation at point b?
2900
3200
2800
3100

Explanation:

Question 1

Step1: Identify known elevations

We know two contour lines: 3500' (near point X) and 3000' (near point Y). Let's count the number of contour intervals between them.
Looking at the map, the number of contour lines between 3500' and 3000' is 4 (since from 3500 to 3000, we have to go down 4 intervals? Wait, no, let's check the distance. Wait, the vertical difference is \( 3500 - 3000 = 500 \) feet. Now, how many contour lines are between them? Let's see, from 3500, the next line would be 3500 - CI, then 3500 - 2CI, etc., until we reach 3000. Wait, actually, the number of intervals between 3500 and 3000: let's count the lines. Let's see, the 3500 line, then the next one, then next, then next, then 3000. So that's 4 intervals? Wait, no, 3500 to 3000: the difference is 500. If we divide 500 by the number of intervals. Wait, maybe I made a mistake. Wait, the options are 1000, 125, 500, 100. Wait, 3500 - 3000 = 500. If the contour interval is 125, then the number of intervals would be \( \frac{500}{125} = 4 \). Let's check: from 3500, subtract 125 four times: 3500 - 125 = 3375, 3375 - 125 = 3250, 3250 - 125 = 3125, 3125 - 125 = 3000. Yes! So that's 4 intervals, each 125 feet. So the contour interval is 125'.

Step1: Determine contour interval

From question 1, we know the contour interval (CI) is 125'.

Step2: Find the elevation of the known line near A

We see a 3000' contour line. Point A is above the 3000' line. Let's count the number of contour lines above 3000' to A. Wait, looking at the map, the 3000' line, then the next line is 3000 + 125 = 3125, then 3250, then 3375, then 3500? Wait, no, point A is on a line that's 3 intervals above 3000? Wait, no, let's see: the 3000' line, then moving towards A (which is on the left side), the contour lines are closer. Wait, the 3000' line, then the next line is 3000 + 125 = 3125, then 3250, then 3375, then 3500. Wait, point A is on the line that is 3 intervals above 3000? Wait, 3000 + 3*125 = 3000 + 375 = 3375? No, wait, maybe I got the direction wrong. Wait, the 3500' line is at the top, then 3500 - 125 = 3375, 3375 - 125 = 3250, 3250 - 125 = 3125, 3125 - 125 = 3000. So moving from 3500 down to 3000, the lines are 3500, 3375, 3250, 3125, 3000. So point A is on the 3375' line? Wait, no, let's check the options. The options are 3400, 3375, 3600, 3300. So 3375 is an option. Let's confirm: the contour interval is 125, so from 3000, each line up is +125. So 3000, 3125, 3250, 3375, 3500. So point A is on the 3375' contour line.

Step1: Determine contour interval

From question 1, CI = 125'.

Step2: Find the elevation of the known line near B

The 3000' line is near Y. Point B is below the 3000' line. Let's count the number of contour lines below 3000' to B. The 3000' line, then the next line down is 3000 - 125 = 2875? No, wait, no: wait, the contour lines: from 3000, moving towards B (which is below Y), the next line is 3000 - 125 = 2875? No, that can't be. Wait, maybe I messed up. Wait, the 3000' line, then the next line towards B (which is in the direction of lower elevation) would be 3000 - 125 = 2875? No, the options are 2900, 3200, 2800, 3100. Wait, maybe the contour interval is 100? No, question 1's answer is 125. Wait, no, maybe I made a mistake in question 1. Wait, let's recheck question 1. The distance between 3500 and 3000 is 500. If the contour interval is 125, then 500 / 125 = 4 intervals, which matches the number of lines between them. So CI is 125. Then, point B: the 3000' line, then moving towards B (downhill), the next line is 3000 - 125 = 2875? No, that's not an option. Wait, maybe the 3000' line, then the line above B is 3000, and B is on a line that's 1 interval below 3000? Wait, 3000 - 125 = 2875, not an option. Wait, maybe the contour interval is 100? No, 500 / 100 = 5 intervals, but the number of lines between 3500 and 3000 is 4. Wait, maybe I miscounted the lines. Let's see the map: the 3500' line, then three more lines, then 3000'? Wait, 3500, then 3400, 3300, 3200, 3100, 3000? No, that would be 5 intervals, 500 / 5 = 100. Oh! Maybe I made a mistake in question 1. Let's re-express: if the contour interval is 100, then 3500 - 3000 = 500, 500 / 100 = 5 intervals. So the number of lines between 3500 and 3000 would be 5. Let's check the map: 3500, then 3400, 3300, 3200, 3100, 3000. That's 5 intervals. So maybe the contour interval is 100? Wait, the options for question 1 are 1000, 125, 500, 100. So 100 is an option. Let's recheck question 1. If CI is 100, then 3500 - 3000 = 500, 500 / 100 = 5 intervals. So the number of contour lines between 3500 and 3000 is 5. Let's see the map: the 3500' line, then 5 lines down to 3000. So that's 5 intervals, so CI is 100. Oh, I see, I miscounted the lines earlier. So question 1's answer is 100'. Let's correct that.

Correcting Question 1:

Answer:

125'

Question 2