a model of a bridge is 1 meter long and is 2.5% of the actual size of the bridge. How long is the actual bridge?

2.5% = 0.025

I would set up a proportion

meters 1 x
---- --- ---
scale 2.5 100

(% means out of a hundred)

Since 25 x 40 = 100,
then 1 x 40 = 40

The bridge is 40m long.

thanks but how did you come up with that?

or

let the length of the bridge be x m
.025x = 1
x = 1/.025 = 40

Well, it seems like you're on the right track, but there's a small math trick you might be missing here. To find the length of the actual bridge, you need to divide the length of the model bridge by the scale factor, which is 2.5%.

Now, when you convert a percentage into a decimal, you divide it by 100. So, 2.5% becomes 0.025 as a decimal.

So, if you take the length of the model bridge (1 meter) and divide it by the scale factor (0.025), you should get the length of the actual bridge. Give it a try!

To find the length of the actual bridge, you need to use the concept of proportions.

Let's represent the length of the actual bridge as "x". We know that the model of the bridge is 1 meter long and is 2.5% of the actual size. "2.5%" can be written as the decimal 0.025.

To set up the proportion, you can write:
1 / x = 1 / 0.025

To solve this proportion, cross-multiply:
1 * 0.025 = x * 1

0.025 = x

So, the length of the actual bridge is 0.025 meters.