A worked example: 12 + 8 and 100 − 36
Enter 12 and 8 with the Add operation and the basic math calculator returns 20. Switch the same calculator to Subtract with 100 as the first number and 36 as the second, and it returns 64. Both are exact — with only two operands and one of four operations, there is no intermediate rounding to worry about; the displayed result is the full result.
The formula: decimal arithmetic without floating-point drift
Internally the calculator converts both inputs to a decimal type rather than using native floating-point math directly, applies whichever of the four operations was selected, then rounds the outcome to 10 decimal places before displaying it to 4. For 100 − 36 that is simply 100 minus 36, computed as exact decimals, giving 64 with nothing after the decimal point to round away.
A worked example: 6 × 7 and 180 ÷ 4
Multiply 6 by 7 and the result is 42. Divide 180 by 4 and the result is 45 — a division that happens to come out even, with no remainder or repeating decimal to display. Try 180 divided by 4 with the operands swapped to 4 divided by 180, though, and the result is a long decimal rather than a whole number, since not every division lands on an integer the way 180 ÷ 4 does.
Why the four-operation limit is a feature here
A calculator that only ever does one operation at a time on two numbers cannot silently misparse an expression's order of operations — there is no order to get wrong, because there is only ever one operation. That makes results like 6 × 7 = 42 or 180 ÷ 4 = 45 completely unambiguous, which is exactly the point for quick single-step arithmetic. The moment a calculation needs more than one operation chained together, or needs something beyond the four basic operations — a square root, a power, a trig function — that is the point to reach for a calculator built to evaluate a full expression instead.