Nutrient Agar dry mix 100g - makes 80x30ml plates
MEA80-100g

Ingredients per 100g of the mix:
- Agar Agar: 47.6g
- Barley Malt Extract: 47.6g
- Dry Yeast: 4.8g

100g makes  2400ml = 80 Petri Dishes (90mm) [ about 30ml/plate]

30ml water and 1.25g of dry mix per plate required 

eg 20 plates = 20 x 30ml water = 600ml water ; 20 x 1.25g = 25g of dry mix

Mix until disolved/evenly mixed . Heat to at least 60°C . Hold at this temp for 5 min to "pasturise". Pour plates.

Also refer to own company/school procedure.