内容正文:
乘整十数、整百数①
WPS,a click to unlimited possibilities
数学学科 三年级 第一学期 第二单元
1
口答
(1)3个十是( )。
(2)50是( )个十。
(3)10个十是( )。
(4)200是( )个十;
200是( )个百。
30
5
100
20
2
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
4×30是多少?
4个30相加
30
+ 30
+ 30
+ 30
=120
4×30=120
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
4×30是多少?
4个3是12
4个3十是12个十
4×3 =12
4×30=120
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
4×30是多少?
4个30相加
30
+ 30
+ 30
+ 30
=120
4×30=120
4个3是12
4个3十是12个十
4×3 =12
4×30=120
0= 0
试一试(课本P10)
①像小亚那样计算
5×30
4×60
3×70
6×50
4×80
7×20
2×90
8×70
试一试(课本P10)
①像小亚那样计算
4×60
60+60+60+60=240
4×60=240
7×20
20+20+20+20+20
+20+20=140
7×20=140
2×90
90+90=180
8×70
70+70+70+70+70
+70+70+70=550
2×90=180
8×70=550
×
560
560
试一试(课本P10)
②像小巧那样计算
6×4 =
6×40=
4×6 =
4×60=
7×8 =
7×80=
8×7 =
8×70=
4×9 =
4×90=
5×2 =
5×20=
9×3 =
9×30=
3×8 =
3×80=
24
240
24
240
56
560
56
560
想一想:
从7×9这道题,可以推算出哪些乘法题?
7×90
9×70
7×900
9×700
……
4×60=240
8×70=560
用小亚的方法算
60+60+60+60
=240
4×60=240
用小巧的方法算
4×6 =24
4×60=240
用小亚的方法算
70+70+70+70
+70+70+70+70
=560
8×70=560
用小巧的方法算
8×7 =56
8×70=560
3×30=
30+30+30=90
3×30=90
3×3 =9
3×30=90
90(个)
答:三纸板鸡蛋一共有90个。
练一练(课本P11)
练一练(课本P11)
6×30=
180(个)
答:新世纪小学得到180枚鸡蛋。
7×30=
210(个)
答:时代小学得到210枚鸡蛋。
8×30=
240(个)
答:实验小学得到240枚鸡蛋。
5×30=
150(个)
答:田园小学得到150枚鸡蛋。
如果一箱有300个鸡蛋,
9箱一共有多少个鸡蛋?
9×300=
回顾小结
4个30相加
30
+ 30
+ 30
+ 30
=120
4×30=120
4个3是12
4个3十是12个十
4×3 =12
4×30=120
0= 0
感谢观看
THANK YOU
$$