Its not easy having a mathematics professor as a friend. When she invited you to her house she
says, “All the houses on my side of the street are numbered consecutively in even numbers. There are
Six houses on my Side of my block and sum of their numbers is 9870. You don’t know which block I
live on, and it’s a long street, but I will tell you that I live in the lowest number on my side of the block. What’s the number? Or are you just going to ring the first- numbered doorbell for twenty blocks?  Choose the most appropriate option: A) 22388 B) 2777 C) 199 D) 1640 E) 2912
Given all the number are even consecutive numbers. This is AP.   Formula for sum of numbers = Sn=n2[2a+(n−1)d]Sn=n2[2a+(n−1)d]   Sum = 9870, n = 6, d = 2   9870=62[2a+(6−1)2]9870=62[2a+(6−1)2]   ⇒ 9870 = 3 (2a + 10)   ⇒ 9840 = 6a   ⇒ a = 1640   Answer:1640
<result>D</result>
Its not easy having a mathematics professor as a friend. When she invited you to her house she
says, “All the houses on my side of the street are numbered consecutively in even numbers. There are
Six houses on my Side of my block and sum of their numbers is 9870. You don’t know which block I
live on, and it’s a long street, but I will tell you that I live in the lowest number on my side of the block. What’s the number? Or are you just going to ring the first- numbered doorbell for twenty blocks?