The 10 grams of protein that most of us get from cereal and milk at breakfast, he added, is not enough to get the bodyâs muscle-building machinery working at full throttle. For that, we would need to eat about 25 to 30 grams of protein, the amount in a three-egg cheese omelet.
For example, the prefix kilo means times a thousand or one thousand of the units in question. So  kilometre means one thousand metres and kilogrammeans one thousand grams.
K means Thousand in terms of Money. Many times we see like Rs 5K or 15K. That simply means 5,000 or 15,000. Basically K equals to Kilo and Kilo means THOUSAND. So for sake of convenience we use K instead of thousand. This is just abbreviation form of Kilo.Its just a shorter way to write the figure, and is commonly used these days almost everywhere. The letter always follows the number.