There are 300 people in a book club. 40% of the members are students. How many students should join in so that the number of students occupies 60% of the club?
Find the value of $\frac1{1\times2\times3}+\frac1{2\times3\times4}+\frac1{3\times4\times5}+\cdots+\frac1{17\times18\times19}+\frac1{18\times19\times20}$.
Given a square. Wendy draws 2 quarters whose centers are vertices of the squares as follows. If the area of the white region is $32-8\pi$, find the area of the shaded region.
Numbers are drawn from 1234 integers 1 to 1234. At least how many numbers are drawn at random to ensure that there are two numbers whose difference is 5?