Question

Difficulty: HardSlope and Gradient Calculation

On a topographical map drawn to a scale of 1:50,0001 : 50,000, Point X is situated at an elevation of 150 m150\text{ m} and Point Y is situated at an elevation of 400 m400\text{ m}. If the straight-line distance between Point X and Point Y measured on the map is 5 cm5\text{ cm}, what is the slope gradient between the two points expressed as a percentage?

  1. A
    0.1%0.1\%
  2. 10%10\%Answer
  3. C
    16%16\%
  4. D
    5%5\%

Answer

The slope gradient between Point X and Point Y expressed as a percentage is 10%10\%.
To find the gradient percentage, first calculate the Vertical Interval (VI): 400 m150 m=250 m400\text{ m} - 150\text{ m} = 250\text{ m}. Next, calculate the Horizontal Equivalent (HE): 5 cm×50,000=250,000 cm=2,500 m5\text{ cm} \times 50,000 = 250,000\text{ cm} = 2,500\text{ m}. Expressing VI over HE gives 250 m2,500 m=110\frac{250\text{ m}}{2,500\text{ m}} = \frac{1}{10}. Converting this fraction to a percentage gives 1/10×100%=10%1/10 \times 100\% = 10\%.

Step-by-Step Solution

1
Calculate the Vertical Interval (VI)
VI=400 m150 m=250 m\text{VI} = 400\text{ m} - 150\text{ m} = 250\text{ m}
The Vertical Interval is the difference in elevation between the higher point and lower point.
2
Calculate the Horizontal Equivalent (HE) in meters
HE=5 cm×50,000=250,000 cm=2,500 m\text{HE} = 5\text{ cm} \times 50,000 = 250,000\text{ cm} = 2,500\text{ m}
Multiply the map distance by the scale denominator to find ground distance, then convert centimeters to meters.
3
Compute the slope gradient as a fraction and convert to percentage
Gradient=VIHE=250 m2,500 m=0.10=10%\text{Gradient} = \frac{\text{VI}}{\text{HE}} = \frac{250\text{ m}}{2,500\text{ m}} = 0.10 = 10\%
Gradient percentage is calculated by dividing Vertical Interval by Horizontal Equivalent in identical units and multiplying by 100%100\%.

Key Concept

Slope and Gradient Calculation
Estimated Time:2m 0s
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