(a) State four characteristics of igneous rocks.... | WAEC SSCE - Agricultural Science - 2018 (Essay)

Question 1 Report

(a) State four characteristics of igneous rocks.

(b) The table below illustrates the combined demand and supply schedule for maize.

Use it to answer the questions that follow.

Price (₦)	Quantity of maize demanded (kg)	Quantity of maize supplied (kg)
20	50	340
16	70	300
12	125	250
8	200	200
4	350	130

(i) Draw the demand and supply curves to show the equilibrium price of maize.

(ii) Determine the excess demand for maize at a unit price of ₦4.

(iii) Determine the excess supply for maize at a unit price of ₦12.

Answer

(a) Characteristics of igneous rocks

They are formed by the cooling and solidification of molten magma or lava.
They are crystalline and consist mainly of interlocking mineral crystals.
They are generally hard, compact and resistant to weathering and erosion.
They contain mainly primary minerals and do not occur in layers or strata.

(b)(i) Demand and supply curves for maize

The demand curve slopes downwards from left to right, while the supply curve slopes upwards from left to right. Their point of intersection, E, gives the equilibrium position.

graph — Demand and supply schedules plotted with quantity of maize on the horizontal axis and price on the vertical axis. Point E (200 kg, ₦8) is the equilibrium point.

At equilibrium, quantity demanded equals quantity supplied:

\[Q_d=Q_s=200\text{ kg};\qquad P=\text{₦}8\]

Therefore, the equilibrium price is ₦8 per kg and the equilibrium quantity is 200 kg.

(ii) Excess demand at ₦4 per kg

At ₦4, quantity demanded = 350 kg and quantity supplied = 130 kg.

\[\text{Excess demand}=Q_d-Q_s=350-130=220\text{ kg}\]

Excess demand = 220 kg.

(iii) Excess supply at ₦12 per kg

At ₦12, quantity supplied = 250 kg and quantity demanded = 125 kg.

\[\text{Excess supply}=Q_s-Q_d=250-125=125\text{ kg}\]

Excess supply = 125 kg.

Read lesson note on Rocks (WAEC)

Answer Details