Ratios are everywhere! The scale on a map or blueprint is a ratio. Ingredients sometimes need to be mixed using ratios such as the ratio of water to cement mix when making cement. Watch this tutorial to learn about ratios. Then think of some ratios you've encountered before!
Without a blueprint, it would be really hard to construct a building. Without a road map, you'd be lost! Scale drawings make it easy to see large things, like buildings and roads, on paper. Even a GPS uses scale drawings! Check out this tutorial to learn all about scale drawings.