Find the sum of natural numbers from (26) to (35).
Answer and explanation
Correct answer: 305
There are 10 numbers from 26 to 35. Using the sum formula for an arithmetic progression,
a = 26, d = 1, n = 10
\\(S_n = \frac{n}{2}[2a+(n-1)d]\) = \\(\frac{10}{2}[2(26)+9]\) = \\(5(61) = 305\). Therefore, 305 is the correct answer. A result such as 295 may arise from counting the terms incorrectly or using the wrong last term. Exam tip: For sums of consecutive integers, first determine the number of terms carefully.
Frequently asked questions
What is the correct answer to this question?
305
Why is this the correct answer?
There are 10 numbers from 26 to 35. Using the sum formula for an arithmetic progression,
a = 26, d = 1, n = 10
\\(S_n = \frac{n}{2}[2a+(n-1)d]\) = \\(\frac{10}{2}[2(26)+9]\) = \\(5(61) = 305\). Therefore, 305 is the correct answer. A result such as 295 may arise from counting the terms incorrectly or using the wrong last term. Exam tip: For sums of consecutive integers, first determine the number of terms carefully.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Sum of first n natural numbers.
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