Question by Lonnie: This is a two part algebra question with ratios, can you solve it?
The Port Austin Reef Lighthouse is 60 feet tall. Use the height of the model given to complete the scale. How many times taller than the model is the actual lighthouse?
Height: 10 inches
scale: 2in.:__ft?
and the second one is
height: 6 inches
scale: 2in.:__ft?
I will give max points for showing how to get these? Thanks
Best answer:
Answer by Gannok
The easiest and first thing to do, is change the 60 feet into inches. This allows you to make a direct comparison.
So 60 x 12 = 720 inches
Now, with the ratio we have:
720 inches : 10 inches
If we divide both sides by 10, we get:
72 inches : 1 inch
This means, that for ever 72 inches of real height, we get 1 inch of model height. So if we have a scale of:
2 inches : ? feet
it’s easy to figure out. We take our ratio 72:1, multiply by 2, and get:
144 : 2
But since we need the 144 in feet, not inches, we divide 144 by 12 inches, and get: 12 feet.
So for the first answer, the answer is: 2 inches : 12 feet
The second one is just the same, only instead of 720 : 10, it’s now 720 : 6. But we get the solution in the same way. We divide both sides. In this case, by 6. So:
720/6 : 6/6 = 120 inches : 1 inch
We now apply the same rules as before. If we want the 2 inches : ? ft we multiply, again by 2.
So, 120 x 2 : 1 x 2 = 240 inches : 2 inches
Again we need it in feet, so 240 / 12 = 20 feet
So the answer is 2 inches : 20 feet.
Know better? Leave your own answer in the comments!