Two poles of the height 15 m and 20 m stand vertically upright on a plane ground. If the distance between their feet is 12 m, find the distance between their tops. A. 11 m B. 12 m C. 13 m D. 14 m
C
This problem involves two vertical poles of different heights standing on level ground. We are given the heights of the poles and the distance between their feet. We need to find the distance between their tops. This situation can be visualized as a right-angled triangle where the distance between the tops is the hypotenuse.
Let's represent the two poles as vertical lines. Pole 1 has a height of 15 m, and Pole 2 has a height of 20 m. They are standing on a plane ground, and the horizontal distance between their feet is 12 m.
To find the distance between their tops, we can draw a line segment connecting the tops of the two poles. Now, imagine drawing a horizontal line from the top of the shorter pole to the vertical line of the taller pole. This creates a right-angled triangle.
The height of Pole 1 is \(h_1 = 15\) m.
The height of Pole 2 is \(h_2 = 20\) m.
The difference in height is \( \Delta h = h_2 - h_1 = 20 \text{ m} - 15 \text{ m} = 5 \text{ m} \).
This difference in height, 5 m, is one leg of our right-angled triangle.
We have a right-angled triangle with:
According to the Pythagorean theorem, in a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.
The formula is \(a^2 + b^2 = c^2\), where \(a\) and \(b\) are the lengths of the legs, and \(c\) is the length of the hypotenuse.
In our case, \(a = 12\) m and \(b = 5\) m. We want to find \(c = d_{tops}\).
So, we have:
\( d_{tops}^2 = (\text{distance between feet})^2 + (\text{difference in height})^2 \)
\( d_{tops}^2 = (12 \text{ m})^2 + (5 \text{ m})^2 \)
\( d_{tops}^2 = 144 \text{ m}^2 + 25 \text{ m}^2 \)
\( d_{tops}^2 = 169 \text{ m}^2 \)
To find \(d_{tops}\), we take the square root of 169:
\( d_{tops} = \sqrt{169 \text{ m}^2} \)
\( d_{tops} = 13 \text{ m} \)
The distance between the tops of the two poles is 13 m.
| Description | Value |
|---|---|
| Height of Pole 1 | 15 m |
| Height of Pole 2 | 20 m |
| Distance between feet | 12 m |
| Difference in height | \(20 - 15 = 5\) m |
| Distance between tops (Hypotenuse) | 13 m |
| Concept | Explanation | Relevance Here |
|---|---|---|
| Vertical Poles | Stand perpendicular to the ground (90 degrees). | Forms the vertical sides in the diagram. |
| Plane Ground | Flat surface, forms the horizontal side. | Ensures the distance between feet is a horizontal line. |
| Right-Angled Triangle | A triangle with one 90-degree angle. | The geometry of the poles and distance creates one. |
| Pythagorean Theorem | \(a^2 + b^2 = c^2\) in a right triangle. | Used to find the distance between the tops. |
The same principle can be applied to similar problems involving vertical heights and horizontal distances. For example:
In all these cases, identifying or constructing a right-angled triangle is key to using the Pythagorean theorem effectively to find unknown lengths.
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