Find the value of the expression 1 - 2 + 3 - 4 + 5 - 6 + 7 + .... upto 100…
2025
Find the value of the expression 1 - 2 + 3 - 4 + 5 - 6 + 7 + .... upto 100 terms . ?
- A.
-150
- B.
-60
- C.
-100
- D.
-50
Attempted by 164 students.
Show answer & explanation
Correct answer: D
Solution: Group the terms into pairs as (1 - 2) + (3 - 4) + ... + (99 - 100).
Each pair equals -1 because an odd number minus the next even number gives -1 (for example, 1 - 2 = -1, 3 - 4 = -1).
There are 100 terms, so there are 100/2 = 50 such pairs.
Total sum = 50 × (−1) = −50.
Final answer: -50