Short verdict
Choose the service that makes a non-sensitive calculation easiest to audit. DeepSeek or another free assistant can produce an explanation, but the decisive checks are the formula, units, rounding rule and an independent recalculation. This guide does not establish a model accuracy ranking.
Free AI chat and DeepSeek can both be considered for everyday arithmetic help. The useful question is whether an answer is easy to verify. An impressive explanation does not rescue a wrong input, an omitted delivery charge or rounding performed at the wrong stage.
The example here is fictional, not a financial recommendation or a real invoice. Provider sources were reviewed on October 8, 2026; we did not run a benchmark or establish which model is more accurate.
Give both services an unambiguous problem
Suppose an order contains three notebooks at $4.80 each. A 10% discount applies to the notebooks only. Delivery costs $2.50, and there is no tax in this invented example. Ask for the final amount, each calculation step and the point at which rounding occurs.
The checkable calculation is $14.40 for the notebooks, minus $1.44, plus $2.50: a final $15.46. This answer comes from ordinary arithmetic, independently of any chatbot response. If an assistant discounts delivery as well, it has solved a different problem.
| Check | Expected evidence |
|---|---|
| Quantities | Three items, not one |
| Discount base | Merchandise only |
| Delivery | Added after the discount |
| Units | Dollars throughout |
| Final amount | $15.46 under the stated assumptions |
Test clarification before complexity
Now remove the sentence defining what receives the discount. A careful assistant should identify the ambiguity or explain which assumption it uses. Merely matching the earlier total would not prove that it noticed the missing condition.
Next, request a reusable formula with quantity, unit price, discount rate and delivery as separate variables. This exposes whether the assistant understands the structure rather than repeating one set of numbers. Check the formula by setting the discount to zero and then delivery to zero. These small substitutions are more revealing than an unnecessarily elaborate word problem.
Keep the input artificial
DeepSeek’s privacy notice describes collection of prompts and uploads, and distinguishes its own services from downstream applications operated by other developers. A site using a DeepSeek model name can therefore involve another operator’s rules. Check the service address and policy rather than assuming every interface has the same data handling.
Use invented quantities for a comparison. There is no need to upload a real customer invoice, payment record or private account number to check whether a formula is explained clearly. A free label does not establish a confidential processing arrangement.
Prefer a reproducible answer
Choose DeepSeek or another free assistant if it separates inputs, labels assumptions and revises the correct step after a challenge. Preserve your own calculation outside the chat, using a calculator or spreadsheet for the numeric check. If the explanation and independent result disagree, resolve the inputs before acting on either answer.
Our free AI chat vs Copilot guide covers a different workflow choice. For calculation work, the strongest result is the one another person can reproduce from the stated numbers.
Sources and freshness
This is source-informed editorial analysis, not a hands-on benchmark. Proposed tests are evaluation suggestions, not reported results. Features, prices, limits, and policies can change; verify current official terms before acting.
Independent publication; verify current details with each provider.