The first five rows of a number array are shown below?

The first five rows of a number array are shown below.

Row 1 1
Row 2 2 3
Row 3 4 5 6
Row 4 7 8 9 10
Row 5 11 12 13 14 15

What is the sum of the numbers in row 8?


1. 224

2. 231

3. 260

4. 175

feak
Asked Dec 03, 2009
3
the1ndonliladi
Answered Feb 03, 2010
As the1ndonliladi said, the answer is 3, but I will explain to you the process of getting there.

Each row is the previous row, plus the row number. So row 1 is 1, then 1+1 is 2, so the next row is 2, and it's 1 number longer, so you take the last number and add 1, getting you 2 3. So 2+2 is 4, and 2+3 is 5 so then we have 4 5 and one number longer adding one onto the last number gets us 4 5 6. If we keep this up, eventually the all the rows start just going in numerical order (like rows 3 and 5), so row 8 ends up being 29 30 31 32 33 34 35 36, which adds up to 260.
Oni_Kami
Answered Feb 03, 2010

TIP: If it's not your answer to this question, please click "Leave a Comment" button under the question to communicate with the question owner.

Categories