A railwway tunnel in shape of circle has diamet 4.8m. AB is a horizontal line representing the ground rails are laid on and is 3.2m. How do you calculate the height from ground to top of tunnel?

Answer 1

-- Draw a line from the center of the circle to the end of the horizontal rail-platform.

That line is a radius of the circle, so it's 1/2 the length of the diameter.

-- Draw a line from the center of the circle straight down, perpendicular to the

horizontal rail-platform.

Now you have a right triangle inside the circle. The hypotenuse is a radius of the circle ...

you know it's length. The base is 1/2 of the rail platform ... you know how long that is.

So you have 2 sides of the right triangle.

-- Now you can calculate the 3rd side of the right triangle. That's the triangle's height,

and it's the vertical distance from the rail platform to the center of the circle.

-- Plus one more radius of the circle takes you the rest of the way to the top of the tunnel.

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