In a seating arrangement, 5 people (A, B, C, D, E) sit in a row. A and B must sit together, and C cannot sit at the ends. How many arrangements are possible?
What is the sum of the first 20 terms of the arithmetic sequence 3, 7, 11, ........?
A rectangle's length is twice its breadth. If the perimeter is 60 cm, what is its area?
In how many ways can 5 identical balls be distributed into 3 distinct boxes?
The roots of the quadratic equation $x^2 - 6x + k = 0$ are real and distinct. How many integer values of $k$ are possible if $k$ is positive?
A shopkeeper sells an item at a 20% discount but still makes a 20% profit. If the cost price is Rs. 100, what is the marked price?