A few days ago
Anonymous

Geometry question, need help please?

Based on the pattern, make a conjecture about the sum of the first 40 positive even numbers.

2 = 2 = 1*2

2 + 4 = 6 = 2*3

2 + 4 + 6 = 12 = 3*4

2 + 4 + 6 + 8 = 20 = 4*5

2 + 4 + 6 + 8 + 10 = 30 = 5*6

A. The sum is 40*40

B. The sum is 40*41

C. The sum is 39*40

D. The sum is 41*42

Top 3 Answers
A few days ago
hayharbr

Favorite Answer

Since the sum of the first four was 4 * 5, and the sum of the first five was 5 * 6, the sum of the first 40 if it follows the pattern should be 40 * 41
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A few days ago
Mike M
The answer would be B

5*6=30=2+4+6+8+10 (there are 5 integers to sum so let’s call the number of integers to sum “X”)

Therefore the answer is X*X+1, so for 40 integers, it would be 40*41 (B)

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A few days ago
TurtleFromQuebec
The sum of the first 2 even numbers is 2*3

The sum of the first 3 even numbers is 3*4

The sum of the first 4 even numbers is 4*5

The sum of the first N even numbers is … ?

See the pattern yet?

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