Consider the sequence of numbers beginning 23, 27, 28, 32, 33... It continues in such a way that by adding 5 to the nth term, one obtains the (n + 2)th term. What is the sum of the first 18 members of this sequence?
Options:
A) 878  B) 900  C) 788  D) 810  E) 1022
I would split them up like this.   23 28 33 and so on (9 terms)....the 10th term = 23+8*5= 
<gadget id="calculator">23+8*5</gadget>
<output>63</output>
63   27 32 37 and so on (9 terms)......the 9th term= 27+8*5= 
<gadget id="calculator">27+8*5</gadget>
<output>67</output>
67   Since the distance between any two numbers is the same we can use arithmetics   first+last/2 times no of numbers= the sum   (23+63)/2 * 9= 
<gadget id="calculator">(23+63)/2 * 9</gadget>
<output>387</output>
387   (27+67)/2 * 9= 
<gadget id="calculator">(27+67)/2 * 9</gadget>
<output>423</output>
423= 810   810
<result>D</result>
Consider the sequence of numbers beginning 23, 27, 28, 32, 33... It continues in such a way that by adding 5 to the nth term, one obtains the (n + 2)th term. What is the sum of the first 18 members of this sequence?