We are using one of our chemistry kits today.
I basically pulled it out, had a look at the booklet (a collection of science activities without ANY explanation as to what is going on chemically...) and said, "Here, pick something." lol. I had noticed one of the activities was "Slime" and mentioned it. So, he found it and is doing it on his own. Except for... I'm not sure where this kit was made, but it says to use 200g of cornstarch. Here in North America, I'm pretty sure nobody measures cornstach in grams. I said we could look online and asked him how we would go about searching for how to measure it in mL. His search didn't quite bring us to what we needed, so I added in cooking.
Well... The table we got to was rather complicated and had the conversions for cornstarch but not specifically 200g. Or even 100g. The easiest number to work with was 40g. This meant knowing that 40g fit 5 times into 200g, then multiplying the 1/3 cup equivalent by 5 and THEN figuring out they wanted 1 2/3 cups.
I LOVE it when practical things show up like this that show we do need certain math skills!!