An arithmetic sequence is a sequence of numbers a1, a2, a3,... where an - an-1 has the same value for every n. For example, 2, 4, 6, 8, 10,....is such a sequence where the difference between any 2 consecutive numbers is 2. Given, a, b, c, d, and e are consecutive numbers in such a sequence and a + b + c + d + e = 90. What is the value of c?
Erin remembers that her mother's birthday is after 18th but before 23rd of February. Her sister Ammaarah remembers that her mother's birthday is before 27th and after 21st of February. On which date of February is their mother's birthday?