Question

15．計(jì)算小數(shù)加減法時(shí)，先把小數(shù)點(diǎn)對(duì)齊，然后從個(gè)位算起．×（判斷對(duì)錯(cuò)）

Answer 1

分析 小數(shù)加法的法則：小數(shù)加法的法則與整數(shù)加法的法則一樣，也是相同的數(shù)位對(duì)齊．由于小數(shù)中有小數(shù)點(diǎn)，因此，只要小數(shù)點(diǎn)對(duì)齊，相同的位數(shù)就必然對(duì)齊了．
步驟：①把各個(gè)加數(shù)的小數(shù)點(diǎn)上下對(duì)齊；②按照整數(shù)加法的法則進(jìn)行計(jì)算，從右邊最末一位加起，滿十進(jìn)一；③和（計(jì)算結(jié)果）的小數(shù)點(diǎn)要與加數(shù)的小數(shù)點(diǎn)上下對(duì)齊．
小數(shù)減法的法則：小數(shù)點(diǎn)對(duì)齊，相同位數(shù)對(duì)齊．
步驟：①把被減數(shù)和減數(shù)的小數(shù)點(diǎn)上下對(duì)齊；②按照整數(shù)減法的法則進(jìn)行計(jì)算，從右邊最末一位減起，不夠減時(shí)，借一當(dāng)十；③差的小數(shù)點(diǎn)要與被減數(shù)、減數(shù)的小數(shù)點(diǎn)上下對(duì)齊．
依此即可求解．

解答 解：計(jì)算小數(shù)加減法時(shí)，要對(duì)齊小數(shù)點(diǎn)，從末位算起．
所以題干說(shuō)法錯(cuò)誤．
故答案為：×．

點(diǎn)評(píng) 本題主要考查小數(shù)加減法計(jì)算方法．關(guān)鍵是熟練掌握計(jì)算法則正確進(jìn)行計(jì)算．