第3課時(shí)約分和最簡(jiǎn)分?jǐn)?shù)1.選擇題。(把正確答案的序號(hào)填在括號(hào)里)(1)下列各數(shù),不是最簡(jiǎn)分?jǐn)?shù)的是()。A.49B.1435C.54(2)一個(gè)最簡(jiǎn)真分?jǐn)?shù),分子和分母相加的和是10,這個(gè)最簡(jiǎn)真分?jǐn)?shù)是()。A.19或37B.28C.73(3)與56相等的分?jǐn)?shù)是()。A.1220B.2530C.2542(4)小于59而大于512的分?jǐn)?shù)有()個(gè)。A.1B.2C.無數(shù)2.把下面各分?jǐn)?shù)約分。3545 =1624 =2718 =5533 =2639 =2575 =3660 =1254 =3.比較下面每組中兩個(gè)分?jǐn)?shù)的大小。4.計(jì)算下面各題。37+47= 79-49=78-38=23+23= 65+45= 116-56=74+54= 135-65= 29+59=5.艷艷用她零花錢的720買了書,又用零花錢的920買了學(xué)習(xí)用品。買書和學(xué)習(xí)用品的錢一共占總錢數(shù)的幾分之幾?答案提示1.(1)B(2)A(3)B(4)C2.79233253231335293.=4.113124321375795.720+920 = 1620 = 45