In a practice session, marks from (1) to (15) are scored in the first (15) steps, and no marks are scored in the next (10) steps. What is the total score?
Answer and explanation
Correct answer: 120
The marks in the first 15 steps are 1 through 15, so their sum is \(\frac{15\times16}{2}=120\). The next 10 steps contribute zero marks, so they do not change the total. Option 130 would require 10 additional marks, but these steps add zero, not 10. Exam tip: use \(\frac{n(n+1)}{2}\) for the sum of natural numbers from 1 to n.
Frequently asked questions
What is the correct answer to this question?
120
Why is this the correct answer?
The marks in the first 15 steps are 1 through 15, so their sum is \(\frac{15\times16}{2}=120\). The next 10 steps contribute zero marks, so they do not change the total. Option 130 would require 10 additional marks, but these steps add zero, not 10. Exam tip: use \(\frac{n(n+1)}{2}\) for the sum of natural numbers from 1 to n.
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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