Can a calculator give wrong results for 143 + 305 * 70 and how to check it?
Executive summary
A simple arithmetic expression like 143 + 305 * 70 should be evaluated by doing the multiplication first (305×70) and then the addition, giving 21,493 when computed correctly; online order‑of‑operations tools teach and enforce that rule (PEMDAS) and will show the steps [1] [2] [3]. Calculators can appear to give “wrong” answers only when users mistype, when parsing conventions differ, or when the device/software has a bug — the standard diagnostic is to force parentheses, compute steps separately, or cross‑check with another trusted solver [4] [1] [3].
1. Why the expression might trip people up: order of operations is the rule, not optional
The core issue is not arithmetic mystery but operator precedence: multiplication is performed before addition under standard conventions (PEMDAS/MDAS), so the intended calculation is 305×70 then plus 143; education and many online tools explicitly follow that sequence and show step‑by‑step work to make the logic visible [1] [2] [3]. Misreading the expression as (143+305)×70 is a common human error when scanning left to right, which doubles down on why step display matters — the calculators cited are designed to prevent that by showing each operation in order [1] [2].
2. How a calculator can appear to give the “wrong” result
Apparent disagreements arise from three concrete sources documented in practice: user input mistakes (typing 143+30507 or 143+(3057) by accident), different parsing or display conventions that change grouping, and software bugs or implementation choices in evaluation order; mathematical discussion and user reports show calculators sometimes interpret chains of operations differently unless precedence is explicit with parentheses, producing results that surprise users [4]. Trusted online solvers and order‑of‑operations calculators exist specifically to show the stepwise parse so the user can see whether the device applied multiplication before addition or accidentally grouped terms in another way [1] [3] [5].
3. The quick, authoritative check — three practical steps
First, force the intended grouping with parentheses: compute 143 + (305 * 70) explicitly in the calculator to guarantee the multiplication first, then verify the displayed intermediate multiplication; order‑of‑operations solvers show those steps [1] [3]. Second, compute the multiplication separately (305 × 70 = 21,350) and then add 143 to reach 21,493 — using a separate calculation removes parsing ambiguity and is what stepwise solvers teach [1] [2]. Third, cross‑check with a second independent tool or trusted online order‑of‑operations calculator that prints steps; if both show the same two‑step process and result, the arithmetic and parsing are confirmed [1] [3] [5].
4. When to suspect a real bug vs. human error
If multiple reputable calculators and a manual two‑step computation all return the same number, a hardware or software bug is highly unlikely; inconsistent results across tools or a surprising single output usually point back to input or parsing differences rather than fundamental arithmetic failure [4] [1]. Math communities and QA discussions note that calculators sometimes differ in implicit conventions for chained operations, so the diagnostic is to inspect stepwise evaluation and repeat the calculation with parentheses to remove ambiguity [4] [3].
5. Bottom line and recommended practice for absolute certainty
Treat any surprising calculator result as a parsing or input issue until proven otherwise: parenthesize the intended order, compute multi‑step problems piecewise, and use an order‑of‑operations solver that shows work (examples include the PEMDAS solvers and equation solvers referenced) to confirm the parse and arithmetic [1] [2] [3] [5]. For the expression at hand, the conventional and verifiable evaluation is 305×70 = 21,350, then 21,350 + 143 = 21,493; if any tool gives a different number after forcing parentheses and cross‑checking, that tool should be treated as suspect [1] [3].