A vessel has 4 liters and 500 ml of curd. In how many glasses, each of 25ml capacity, can be filled?

Hint: To answer this question we must recall our basic concepts of units of conversion and the fundamental operations involved in unitary method.

Complete answer:
In the question we find the use of two units: liter and milliliter.
Since we know that milliliter is a sub multiple of liter that means it is smaller than liter, we should convert the quantity given to us in milliliters.
We know,
1 liter = 1000 milliliter
Or, 4 liter = 4 x 1000 = 4000 milliliters.
Therefore, total curd provided to us is
= 4000 milliliters + 500 milliliters
= 4500 milliliters.
Now we have to divide these among glasses of 25 milliliters each.
We can apply a unitary method to solve this part of the problem.
 25 milliliters is accommodated in = 1 glass.
Or, 1 milliliter can be accommodated in = \[\dfrac{1}{{25}}\]glass
Or, 4500 milliliters can be accommodated in = \[\dfrac{1}{{25}} \times 4500\, = 180\] glasses.
Hence, the answer is 180 glasses.

Note:
The metric method of measurement - using kilos and meters rather than pounds and feet - is used in everyday life in most countries of the world and everywhere in the scientific and medical communities.
In the metric system, measurement increments are by factors of 10: 100 centimeters make a meter, and 1,000 meters make a kilometer. There are twenty prefixes. Ten prefixes increase the basic unit - gram or meter - by factors of 10.
The mnemonic for the six most commonly used prefixes from kilo to milli is King Henry Didn't Drink Chocolate Milk. You may also include a B for the base unit in the middle of the chart - King Henry Died By Drinking Chocolate Milk. This is the acrostic method of memorizing.