1. Why does the demand curve slopes downward ?
The slope of demand curve moves left to right due to the substitution and income effect ,applicability of the law of diminishing marginal utility new consumers and several; uses of commodities .

2. What are the non price determinants of demand ?
a)  Income in the case of normal goods :-
                           A good is a normal good when demand for it increases in response to an increase in consumer income .Most goods are normal goods .
 b)  Income in the case of inferior goods .
        While most goods are normal there are some goods where the demand falls as consumer income increases ,the good is then an inferior goods .

c)  Preferences and tastes
                  If preferences and change in favour of a product ,demand increases and the demand curve shift to the right ;If tastes change against the product ,demand decreases and the demand curve shift to the left .
e)  Price of substitute goods
              Two goods are substitutes if they satisfy a similar need.
f)   Prices of complementary good
                  Two goods are complementary goods if they tend to be used together .

3. What is called change in quantity demanded ?
A movement along the demand curve cause by a change in price is called ca change in quantity demanded .

4.  What is called change in demand ?
A shift of a demand curve caused by a change in a determinant of demand is called a change in demand .
       

5. Define increase in demand
If there is an increase in the number of buyers ,the demand curve shift rightward from D₁ to D₂ , this is called an increase in demand .

6. Define decrease in demand 

A decrease in the number of buyers causes a leftward shift of the demand curve from D₁ to D₃ this is called a decrease in demand 

7. Define supply .
     The supply of an individual firm indicates the various quantities of a good a firm is willing and able to produce and supply to the market for sale at different possible prices during a particular time period ceteris paribus .

8. Explain the positive causal relationship between price and quantity supplied.
   When two valuable change in the same direction ,they are said to have a positive relationship .This relationship is a causal one because change in price cause changes in quantity supplied .The supply curve (below) illustrate an important relationship ;as price increases quantity supplied also increase
               Supply curve of a firm
     
                     According to the law of supply there is a positive causal relationship between the quantity of a good supplied over a particular time period and its price ,ceteris paribus ;as the price of the good increases ,the quantity of the good supplied also increases;as the price falls ,the quantity supplied also falls ceteris paibus .

9. What is called change in quantity supplied ?
    A movement along the supply curve caused by a change in price is called a change in quantity supplied .
      

10. What is called change in supply ?
       A shift of the supply curve caused by a change in a determinant of supply is called a change in supply