69
32
Six (6)
10.
21
12
32
6 maximum points of intersection
discuss the possible number of points of interscetion of two distinct circle
8
No two circles can intersect more than twice. Each circle can intersect with each other circle. Thus there ought to be 2 × 30 × (30 - 1) intersections. However, this counts each intersection twice: once for each circle. Thus the answer is half this, giving: maximum_number_of_intersections = ½ × 2 × 30 × (30 - 1) = 30 × 29 = 870.
15 mph
The minimum and maximum refers to the number of sunspots.
Six (6)
10.
21
12
With n lines, the maximum number is n*(n-1)/2. The minimum is 0.