Prompt
What is the value of the infinite sum S = 1/2 + 1/4 + 1/8 + 1/16 + ... ? A) 1 B) 2 C) 1/2 D) Diverges to infinity Reply with the letter of the correct option (A, B, C, or D).
Expected output
A
| model | score | output |
|---|---|---|
| openai/gpt-5.6-luna-pro | 100% | A |
| qwen/qwen3.8-max | 100% | A |
| anthropic/claude-opus-5-fast | — | — |