Math Problem Statement

2+4+6+...+70 answer with solution

Solution

This is an arithmetic sequence where the first term a1=2a_1 = 2, the common difference d=2d = 2, and the last term an=70a_n = 70. To find the sum of the sequence, we need to use the formula for the sum of an arithmetic series:

Sn=n2×(a1+an)S_n = \frac{n}{2} \times (a_1 + a_n)

Step 1: Find nn

The number of terms nn in the sequence can be found using the formula for the nth term of an arithmetic sequence:

an=a1+(n1)×da_n = a_1 + (n - 1) \times d

Substitute an=70a_n = 70, a1=2a_1 = 2, and d=2d = 2:

70=2+(n1)×270 = 2 + (n - 1) \times 2

Simplifying:

70=2+2n270 = 2 + 2n - 2 70=2n70 = 2n n=702=35n = \frac{70}{2} = 35

So, there are 35 terms in the sequence.

Step 2: Find the sum

Now, use the sum formula with n=35n = 35, a1=2a_1 = 2, and an=70a_n = 70:

S35=352×(2+70)S_{35} = \frac{35}{2} \times (2 + 70) S35=352×72S_{35} = \frac{35}{2} \times 72 S35=35×36S_{35} = 35 \times 36 S35=1260S_{35} = 1260

Final Answer:

The sum of the sequence 2+4+6++702 + 4 + 6 + \dots + 70 is 12601260.

Would you like more details or have any questions?


Here are 5 related questions:

  1. What is the sum of the sequence 3+6+9++603 + 6 + 9 + \dots + 60?
  2. How do you find the sum of an arithmetic series where the difference is negative?
  3. Can you find the sum of all even numbers between 1 and 100?
  4. What is the 20th term of the sequence 5+10+15+5 + 10 + 15 + \dots?
  5. How can you derive the formula for the sum of an arithmetic series?

Tip: The formula for the sum of an arithmetic sequence can also be derived from the concept of the average of the first and last terms multiplied by the number of terms!

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Math Problem Analysis

Mathematical Concepts

Arithmetic Sequences
Summation

Formulas

Sum of arithmetic series: S_n = (n / 2) × (a_1 + a_n)
Formula for the nth term of an arithmetic sequence: a_n = a_1 + (n - 1) × d

Theorems

Arithmetic Series Summation Formula

Suitable Grade Level

Grades 6-8