Evaluate and correct to two decimal places, 75.0785 - 34.624 + 9.83

Question analysis: We need to add and subtract decimals, then round the result to 2 decimal places.

Concept: Line up the decimal points. Do the subtraction first, then the addition (working left to right). Round at the very end, not before.

Step 1: Subtract

75.0785 − 34.6240 = 40.4545

Step 2: Add

40.4545 + 9.8300 = 50.2845

Step 3: Round to 2 decimal places

50.2845 → look at the third decimal digit, which is 4. Since 4 is less than 5, we keep the second decimal digit as it is.

50.2845 ≈ 50.28

Why not the other options?

• B (50.29) comes from rounding up wrongly, perhaps by rounding too early (e.g., 50.2845 → 50.285 → 50.29). That is a double-rounding error.
• A and D (about 30.6) come from subtracting 9.83 instead of adding it, or from a sign error.

Exam tip: Never round in the middle of the working. Keep all the decimal places until the last step, and only look at the digit right after the one you are rounding to. Here, only the 4 matters, not the 5 after it.