The two sides of a parallelogram are given by the vectors $A = 2i - 3j$ and $B = 3i + 2j$. The area of the parallelogram is

In a BOD test, 5 ml of wastewater is diluted with pure water to fill a 300 ml BOD bottle. The initial and final dissolved oxygen contents of the mix are 9.0 mg/l and 7.0 mg/l respectively. The BOD of the wastewater, in mg/l, is

Dilatancy of rock is associated with

A bord and pillar panel having square pillars is designed for 30% extraction during development. If the gallery width is 5 m, the side of the pillar in m is ______.

Low shock and high gas pressure explosive is generally used for blasting of

A gas mixture contains CH$_4$, C$_2$H$_6$ and H$_2$ with respective concentrations of 75%, 15% and 10% by volume. The lower explosibility limit of CH$_4$, C$_2$H$_6$ and H$_2$ are 5.0%, 3.3% and 4.2% respectively. The lower explosibility limit of the gas mixture, in percentage, is ______.

Intake air containing 0.2% methane enters a section of an underground mine where emission rate of methane is 0.05 m$^3$/s. Assuming that the threshold limit value of methane is 1.25%, the minimum quantity of fresh air required in m$^3$/s is ______.

In a fully mechanised bord and pillar mining system, winning of coal and its transportation from the face is commonly carried out with the combination of

An underground coal mine employing 1200 persons experiences 2 fatal injuries, 6 serious injuries and 8 reportable injuries during the year 2013. The total injury rate per 1000 persons employed for the year is ______.

Out of the support categories given for an underground coal mine, identify the ‘active support’.