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Sng kin kinh nghim mn ton lp 3 n tp

v s t nhin

Ngy son

3/4/2011

Ngy dy: Th ba ngy 5/4/2011

TON

Tit 152: n tp v s t nhin

A. MC TIU:

Gip HS n tp v:

-c, vit s trong h thp phn.

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- Hng v lp, gi tr ca ch s ph thuc vo v tr ca ch s trong 1 s c

th.

- Dy s t nhin v 1 s c im ca n.

B. CHUN B.

- Bng phu.

C. CC HOT NG DY HC:

I. n nh t chc.

II. Kim tra bi c:

Gi HS ln cha bi tp gi trc.

III. Dy bi mi:

H ca thy H ca tr

1. Gii thiu:

2. Hng dn HS n tp:

+ Bi 1:Cng c v cch c, vit s

vo cu to thp phn ca 1 s.

-GV hng dn HS lm mu 1 cu trn

lp.

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HS: T lm tip cc phn cn li ri cha

bi.

+ Bi 2:GV hng dn HS quan st k

phn mu trong SGK.

HS: Tip tc lm cc phn cn li v cha

bi.

VD: 5794 = 5000 + 700 + 90 + 4

20292 = 20000 + 200 + 90 + 2

+ Bi 3: HS: T lm ri cha bi.

a) Cng c vic nhn bit v tr ca tng

ch s theo hng v lp.

b) Cng c vic nhn bit gi tr ca tng

ch s theo v tr ca ch s trong 1 s

c th.

+ Bi 4: Cng c v dy s t nhin v

1 s c im ca n.

HS: Nu li dy s t nhin ln lt tr

li cc cu hi a, b, c.

+ Bi 5: HS: Nu yu cu ca bi v t lm.

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- 3 HS ln bng cha bi.

- GV c th hi HS:

+ Hai s t nhin lin tip hn km

nhau my n v

HS:1 n v.

+ Hai s chn (l) lin tip hn km

nhau my n v

HS: 2 n v.

a) 67, 68, 69.

798, 799, 800.

999, 1000, 1001

b) 8, 10, 12

98, 100, 102

998, 1000, 1002

c) 51, 53, 55

199, 201, 203

997, 999, 1001

- GV nhn xt, cho im nhng HS lm

ng.

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IV. Cng c: - Nhc li ND bi.

- Nhn xt gi hc.

V. Dn d: - V nh hc bi.