Marks obtained by $$100$$ students in an examination are given in the table

What would be the mean, median, and mode of the marks obtained by the students?

A simple random sample of $$100$$ observations was taken form a large population. The sample mean and the standard deviation were determined to be $$80$$ and $$12,$$ respectively. The standard error of mean is ______.

In a given day in the rainy season, it may rain$$70$$% of the time . If it rains, chance that a village fair will make a loss on that day is $$80$$%. However, if it does not rain, chance that the fair will make a loss on that day is only $$10$$%. If the fair has not made a loss on a given day in the rainy season, what is the probability that it has not rained on that day?

If $$\,\phi = 2{x^3}{y^2}{z^4}$$ then $${\nabla ^2}\phi $$ is