High School

The boundary of a mine is plotted on a scale of 1:2000. If a planimeter measures the plotted area as 58 cm², what is the actual mine area in m²?

(a) 5800
(b) 11600
(c) 23200
(d) 29000

Answer :

To determine the actual area of the mine based on the given scale and the measured area, we can follow these steps:

  1. Understanding the Scale: The scale given is 1:2000, which means 1 unit on the map represents 2000 units in actual size.

  2. Planimeter Measurement: The area measured by the planimeter is 58 cm². This is the area on the map or the plotted area.

  3. Converting Map Area to Actual Area:

    Since the map is at a scale of 1:2000, each linear dimension on the map is 1/2000th of the actual size. Therefore, the area is scaled by the square of this factor.

    • The conversion factor for the area is [tex](2000)^2 = 4,000,000[/tex].

    • Therefore, the actual area [tex]A[/tex] in cm² is calculated as:

      [tex]A = 58 \text{ cm}^2 \times 4,000,000 = 232,000,000 \text{ cm}^2[/tex]

  4. Converting cm² to m²:

    There are 10,000 cm² in 1 m². To convert cm² to m², divide by 10,000.

    • So,
      [tex]\frac{232,000,000 \text{ cm}^2}{10,000} = 23,200 \text{ m}^2[/tex]
  5. Selecting the Correct Multiple Choice Option:

    The actual area of the mine in m² is 23,200. Hence, the correct answer is:

    Option (c) 23200.