# Take a look at the following sums: 1 = 1 1 + 3 = 4 1 + 3 + 5 = 9 1 + 3 + 5 + 7 = 16 1 + 3 + 5 + 7 +

Discussion in 'Calculator Requests' started by math_celebrity, Jan 8, 2017.

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Take a look at the following sums:
1 = 1
1 + 3 = 4
1 + 3 + 5 = 9
1 + 3 + 5 + 7 = 16
1 + 3 + 5 + 7 + 9 = 25

a. Come up with a conjecture about the sum when you add the first <i>n</i> odd numbers. For example, when you added the first 5 odd numbers (1 + 3 + 5 + 7 + 9), what did you get? What if wanted to add the first 10 odd numbers? Or 100?

b. Can you think of a geometric interpretation of this pattern? If you start with one square and add on three more, what can you make? If you now have 4 squares and add on 5 more, what can you make?

c. Is there a similar pattern for adding the first n even numbers?
2 = 2
2 + 4 = 6
2 + 4 + 6 = 12
2 + 4 + 6 + 8 = 20

a. The formula is n^2.
The sum of the first 10 odd numbers is 100 seen on our sum of the first calculator

The sum of the first 100 odd numbers is 10,000 seen on our sum of the first calculator

b. Geometric is 1, 4, 9 which is our n^2

c. The sum of the first n even numbers is denoted as n(n + 1) seen here for the first 10 numbers