Official Guide Ed 12. Page 236. Q 157.
For any positive integer n, the sum of the first n positive integers equals [n(n+1)]/2. What is the sum of all the even integers between 99 and 301?
When I solved it, I ignored the first [n(n+1)]/2 part.
I used the MGMAT method of getting sum of a sequence of even numbers:
Total: 300-100+1 = 201/2 = 100.5
Average: 300+100/2 = 200
100.5 * 200 = 20,100. Very close to the correct answer which is 20,200.
What am I doing wrong here?
The OG does use the provided algebraic expression, but I am wondering if this can be solved without it.
For any positive integer n, the sum of the first n positive integers equals [n(n+1)]/2. What is the sum of all the even integers between 99 and 301?
When I solved it, I ignored the first [n(n+1)]/2 part.
I used the MGMAT method of getting sum of a sequence of even numbers:
Total: 300-100+1 = 201/2 = 100.5
Average: 300+100/2 = 200
100.5 * 200 = 20,100. Very close to the correct answer which is 20,200.
What am I doing wrong here?
The OG does use the provided algebraic expression, but I am wondering if this can be solved without it.
