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The given series has six terms. What is the sum of the terms of the series? 1 + 3 + 5 + . . . + 11

2 Answers

3 votes
The rule is +2, so first we find the other two terms.

5 + _ + _ + 11

To find them, add 2 to 5, which gives us 7, so the 4th term is 7, and then add 7 +2, which gives 9, so 9 is the 5th.

Now add all: 1 + 3 + 5 + 7 + 9 + 11 = 36

Your answer is 36.
User Farcaller
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4 votes

Answer: The required sum of the terms is 36.

Step-by-step explanation: We are given that the following series has six terms :

1 + 3 + 5 + . . . + 11.

We are to find the sum of the terms of the series.

We see the following pattern in the consecutive terms of the series :


3-1=5-3= ~~.~~.~~.~~=2.

So, the given series is an ARITHMETIC series with fist term 1 and common difference 2.

We know that

the sum of first n terms of an arithmetic series with first term a and common difference d is given by


S_n=(n)/(2)(2a+(n-1)d).

For the given series,

first term, a = 1 and common difference, d = 2.

Therefore, the sum of first six terms will be


S_6=(6)/(2)(2* 1+(6-1)*2)=3(2+5*2)=3(2+10)=3*12=36.

Thus, the required sum of the terms is 36.

User David Angel
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