Reserve: limestone dip 30, apparent 20 m

Principle: the apparent (vertical) thickness measured in a borehole is converted to true thickness by $t = t_v\cos\delta$; reserve = area $\times$ true thickness.

Given

Dip $\delta = 30^\circ$, apparent thickness $t_v = 20$ m, area $A = 1128.5\ \text{m}^2$.

Calculation

$$\begin{aligned} t &= 20\cos 30^\circ = 20 \times 0.8660 = 17.32\ \text{m} \\ V &= 1128.5 \times 17.32 = 19{,}546\ \text{m}^3 \end{aligned}$$

Answer: reserve of limestone = 19,546 m³ (about 1.95 × 10⁴ m³).

(If the area is the plan area, the volume is $1128.5 \times 20 = 22{,}570\ \text{m}^3$.)