【四捨五入、無條件進位及捨去（小數位及有效數字）】Rounding Off, Rounding Up and Rounding Down (Decimal Places and Significant Figures)
SketchMath 數學團隊 SketchMath Maths Team ｜ 更新 Updated 2026-10-20
四捨五入：看下一位數字，5 或以上就進位，4 或以下就捨去。進位永遠取較大的值，捨去永遠取較小的值，不論下一位是甚麼。計算時要保留完整數值，最後一步才進行近似。Round off to a place by looking at the next digit: 5 or more rounds up, 4 or less leaves it. Round up always goes to the larger value and round down to the smaller, whatever the next digit is. Keep full accuracy until the last step.
沿數線拖動 x：四捨五入至整數的結果，每到半數便跳到下一個整數。 Drag x along the number line: its rounded value to the nearest whole number jumps at every half. 自己試試 → Try it yourself →
近似規則 Rounding Rules
小數位Decimal places (dp)由小數點後計起Count digits after the decimal point
有效數字Significant figures (sf)由第一個非零數字計起Start at the first non-zero digit
⚠️ 中途不要近似 Do not round in the middle後面的步驟要用計數機的完整數值，只在最後答案才近似，否則誤差會累積。Use the full calculator value in later steps and round only the final answer, or errors build up.
⚠️ 保留末尾的零 Keep the zeros6.00 表示 3 位有效數字，6 則不是；題目指定位數時要寫出末尾的零。6.00 shows 3 significant figures, but 6 does not, so write the zeros when the question asks for a number of dp or sf.
小數位由小數點後面計起；有效數字由第一個非零數字計起，與小數點位置無關。
Decimal places count digits after the decimal point; significant figures count from the first non-zero digit, wherever the point is.
當應用題要求最少或最多的整數，例如需要的巴士數目或可買的物品數量。
In word problems that ask for a minimum or maximum whole number, such as buses needed or items you can afford.
有。它可能令答案最後的數字不同，所以要保留完整數值直至最後。
Yes. It can change the last digits of the answer, so keep full values until the end.