If a fair coin is tossed four times, what is the probability of obtaining at least one head?

Forces 90N and 120N act in the directions 120° and 240° respectively. Find the resultant of these forces.

The deviations from the mean of a set of numbers are \((k+3)^{2}, (k+7), -2, \text{k and (} k+2)^{2}\), where k is a constant. Find the value of k.

Find the equation of a circle with centre (2, -3) and radius 2 units.

The first term of a linear sequence is 9 and the common difference is 7. If the nth term is 380, find the value of n.