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What is the sum of the even integers from 18 to 88, inclusive?

Explanation	Calculations	Help
$We first note the key features of our sequence: the first term, the last term, and the constant gap between consecutive even numbers.$	$a_{1} = 18 a_{n} = 88 step = 2$
$Next, we count how many terms appear in this evenly spaced list. By the "Counting Evenly Spaced Integers" rule, we subtract the endpoints, divide by the step, and add one because the list is inclusive.$	$n = \frac{88 - 18}{2} + 1 = \frac{70}{2} + 1 = 35 + 1 = 36$	Theory & Tactics Method Card EVEN1-B Click to view full details
$For an evenly spaced list, the average value equals the mean of the first and last terms.$	$average = \frac{18 + 88}{2} = \frac{106}{2} = 53$
$Finally, we apply the "Sum of Evenly Spaced Integers" rule: the sum equals the average multiplied by the number of terms.$	$sum = 53 \times 36 = (53 \times 30) + (53 \times 6) = 1590 + 318 = 1908$	Theory & Tactics Method Card EVEN1-D Click to view full details

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C

What is the sum of the even integers from 18 to 88, inclusive?

Explanation	Calculations	Help
$We first note the key features of our sequence: the first term, the last term, and the constant gap between consecutive even numbers.$	$a_{1} = 18 a_{n} = 88 step = 2$
$Next, we count how many terms appear in this evenly spaced list. By the "Counting Evenly Spaced Integers" rule, we subtract the endpoints, divide by the step, and add one because the list is inclusive.$	$n = \frac{88 - 18}{2} + 1 = \frac{70}{2} + 1 = 35 + 1 = 36$	Theory & Tactics Method Card EVEN1-B Click to view full details
$For an evenly spaced list, the average value equals the mean of the first and last terms.$	$average = \frac{18 + 88}{2} = \frac{106}{2} = 53$
$Finally, we apply the "Sum of Evenly Spaced Integers" rule: the sum equals the average multiplied by the number of terms.$	$sum = 53 \times 36 = (53 \times 30) + (53 \times 6) = 1590 + 318 = 1908$	Theory & Tactics Method Card EVEN1-D Click to view full details

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C