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3 THI HC SINH GII TON LP 4 V P N THAM KHO
3 THI HC SINH GII TON LP 4 V P N THAM KHO
THI TUYN HC SINH GII
LP 4
Cu 1: (2 im) Tnh nhanh tng sau:
Cu 2: (2 im) Tm tt c cc s c 3 ch s sao cho nu em mi s cng vi 543 th c s c 3 ch s ging nhau?
Cu 3: (2 im) Tm cc phn s ln hn v khc vi s t nhin , bit rng nu ly mu s nhn vi 2 v ly t s cng vi 2 th gi tr phn s khng thay i ?
Cu 4: (2 im) Linh mua 4 tp giy v 3 quyn v ht 5400 ng. Dng mua 7 tp giy v 6 quyn v cng loi ht 9900 ng. Tnh gi tin mt tp giy v mt quyn v?
Cu 5: (2 im) Mt gia nh c 2 ngi con v mt tha t hnh ch nht c chiu rng 20m, chiu di gp 2 ln chiu rng. Nay chia tha t thnh hai hnh ch nht nh c t s din tch l cho ngi con th hai phn nh hn v ngi con c phn ln hn. Hi c my cch chia? Theo em nn chia theo cch no? Ti sao?
HNG DN CHM
TUYN CHN HSG LP 4
Cu 1: (2 im)
Nhn c 2 v vi 3 ta c:
Cu 2: (2 im)
Cc s c 3 ch s ging nhau l:
111; 222; 333; 444; 555; 666; 777; 888; 999. (0,5 im)
Cc s: 111; 222; 333; 444; 555 b loi ( 0,5 im )
V s: 555 - 543 < ***
Cn li ta c:
666 - 543 = 123
777 - 543 = 234 (0,5 im)
888 - 543 = 345
999 - 543 = 456
Vy ta c 4 s l:
123; 234; 345; 456.
p s: 123; 234; 345; 456. ( 0,5 im )
Cu 3: (2 im)
Gi phn s l
Ta c:
Mt khc ( Tnh cht c bn ca phn s )
Do
2 phn s c mu s bng nhau suy ra: a + 2 = a X 2 a = 2
Ta phi tm b
Vy b = 1; 2; 3; 4; 5; 6; 7; 8; 9.
Nn ta c cc phn s sau:
Loi b cc phn s t nhin :
Vy cc phn s cn tm l:
Cu 4: (2 im)
Gi s Linh mua gp i s hng v phi tr gp i tin tc l: 8 tp giy + 6 quyn v v ht 10800 ng. Dng mua 7 tp giy + 6 quyn v v ht 9900 ng. ( 0,5 im )
Nh vy hai ngi mua chnh lch nhau 1 tp giy vi s tin l:
10800 - 9900 = 900 ( ng ) ( 0,5 im )
900 ng chnh l tin mt tp giy
Gi tin mua 6 quyn v l:
9900 - ( 900 x 7 ) = 3600 ( ng) ( 0,5 im ) Gi tin 1 quyn v l:
3600 : 6 = 600 ( ng ) ( 0,5 im )
p s: 900 ng; 600 ng Cu 5: A B A M B
(2 im )
M N
D C
D N C
( 1 ) ( 2 )
Quan st hnh 1 v hnh 2 phn t hnh ch nht u c chung 1 cnh ( chiu di hnh 1; chiu rng hnh 2 ) nn ta ch cn chia cnh kia thnh 2 phn c t s l c. ( 0,25 im )
Nh vy hnh ch nht ABNM c chiu rng l: 20 : ( 2 + 3 ) x 2 = 8 ( m ) ( 0,5 im )
hnh 2 chiu rng AM l :
20 x 2 : ( 2 + 3 ) x 2 = 16 (m ) ( 0,5 im ) Vy cch chia p nht l chia nh hnh 2 v 2 phn t u cn i xy nh.
p s: Chia chiu di thnh 2 phn t s l ( 0,5 im )
(Hnh v 0,25 im )
THI TUYN HC SINH GII
MN TON
LP 4
Cu 1: Tnh nhm cc php tnh sau bng cch hp l.
a) 63000 - 49000
b) 81000 - 45000
Cu 2: Tm x:
a) 1200 : 24 - ( 17 - x) = 36
b) 9 x ( x + 5 ) = 729
Cu 3: Tm s c 2 ch s bit rng nu vit xen ch s 0 vo gia 2 ch s ca s th ta c s mi bng 7 ln s phi tm.
Cu 4: C 3 lp 4A, 4B, 4C trng c 120 cy. Lp 5 B trng c nhiu hn lp 4A 5 cy nhng li km lp 4C 8 cy. Hi mi lp trng c bao nhiu cy?
Cu 5: Tm s nh nht c bn ch s sao cho em chia s cho 675 th c s d l s d ln nht.
HNG DN CHM
TUYN CHN HSG LP 4
MN TON
1) p dng cng thm s b tr v s tr cng mt s n v nh nhau.
a- 63000 - 49000
=(63000 + 1000) - (49000 + 1000)
= 64000 - 50000
= 14000
b- 81000 - 45000
=(81000 + 5000) - ( 45000 + 5000)
= 86000 - 50000
= 36000
2) Tm x:
a- 1200: 24 - ( 17 - x) = 36
50 - ( 17- x) = 36
17 - x = 50 - 36
17 - x = 14
x = 17 - 14
x = 3
b- 9 x ( x + 5) = 729
x + 5 = 729 : 9
x + 5 = 81
x = 81 - 5
3) x = 76
4) Gi s phi tm l: ; khi vit xem ch s 0 v gia 2 ch s ca s ta c s mi l: Phn tch cu to s ta c.
Theo u bi ta c: = 7 x . Phn tch cu to s ta c.
a x 100 + b = 7 x ( 10 x a + b)
a x 100 + b = 70 x a + 7 x b
Cng bt i b + 70 x a 2 v ta c:
30 x a = 6 x b
hay
5 x a = b (1)
V a; b l cc ch s a 0; a 9; b 9
nn t ( 1) ta c a = 1; b = 5
S phi tm l: 15
p s 15
5) Theo u bi ta c s :
Theo s ta thy 3 ln s cy 4A trng l:
120 - ( 5 + 5 + 8) = 102 (cy)
Vy lp 4A trng c l;
102 : 3 = 34 ( cy)
S cy lp 4B trng c l:
34 + 5 = 39 ( cy)
S cy lp 4C trng c l:
39 + 8 = 47 ( cy)
p s: 4A: 34 ( cy)
4B: 39 ( cy)
4C: 47 ( cy)
S nh nht c 4 ch s khi chia cho 675 th thng l 1 v s d ln nht l 674 v:
675 - 1 = 674
S phi tm l:
1 x 675 + 674 = 1349
p s: 1349
THI HC SINH GII LP 4
Mn: Ton
Thi gian: 90 pht
Bi 1:
a/ Sp xp cc phn s sau y theo th t t ln n b:
b/ Tm tt c cc phn s bng phn s sao cho mu s l s c 2 ch s.
Bi 2: Cho dy s 14;16; 18; ....; 94; 96 ; 98.
a/ Tnh tng gi tr ca dy s trn.
b/ Tm s c gi tr ln hn trung bnh cng ca dy l 8. Cho bit s l s th bao nhiu ca dy s trn?
Bi 3: C hai r cam, nu thm vo r th nht 4 qu th sau s cam hai r bng nhau, nu thm 24 qu cam vo r th nht th sau s cam r th nht gp 3 ln s cam r th hai. Hi lc u mi r c bao nhiu qu cam?
Bi 4: Trong mt thng no c 3 ngy th 5 trng vo ngy chn. Hi ngy 26 thng l ngy th my trong tun?
Bi 5: Mt khu vn hnh ch nht c chiu di 35m. Khu vn c m thm theo chiu rng lm cho chiu rng so vi trc tng gp ri v do din tch tng thm 280m2.
Tnh chiu rng v din tch khu vn sau khi m thm.
P N THI HC SINH GII - LP 4
Mn: Ton
Thi gian: 90 pht
Bi 1:( 2 im)
a)V
0,5 im
Nn cc phn s xp theo th t t ln n b l:
0,25 im
b)Ta c
0,25 im
;
;
;
0,5 im
Vy c 5 phn s bng phn s m mu s c 2 ch s l:
EMBED Equation.3
0,5 im
Bi 2:( 2 im)
a/ Dy s cho gm s s hng l:
( 98- 14 ) + 2 + 1 = 43 ( s)
0,25 im
Tng ca dy s cho l:
0,5 im
b/ Trung bnh cng ca dy s trn l: 2408: 43 = 56 0,25 im
Vy s ln hn s Trung bnh cng 8 n v l 56 +8 = 64 0,25 im
Ta c quy lut ca dy l: Mi s hng, k t s hng th hai bng nhn vi s th t ri cng vi 12. 0,25 im
Vy s 64 l s hng th ( 64-12): 2 = 26 0,5 im
Bi 3:( 2 im)
Nu thm 4 qu cam vo r th nht th 2 r bng nhau.
Suy ra r th hai nhiu hn r th nht 4 qu.0.25
Nu thm 24 qu vo r th nht th s cam r th nht gp 3 ln s cam r th hai.
20 qu
Ta c s : 4 qu
S cam r th nht:
S cam r th hai: 0, 5
Nhn vo s ta thy:
S cam r th nht l:
0,25
20 : 2 - 4 = 6 ( qu)
0,25
S cam r th hai l:
0,25
6 + 4 = 10 ( qu)
0,25
p s: 6 qu
02,5
10 qu
Bi 4: ( 2 im)
V tun c 7 ngy nn hai th 5 ca tun lin tip khng th l ngy chn .
Hay gia ba th 5 l ngy chn c hai th nm l ngy l. 0, 5
Th 5 ngy chn cui cng trong thng cch th nm chn u tin l:
7 x 4 = 28 ( ngy) 0, 5
V mt thng ch c nhiu nht 31 ngy nn th 5 v l ngy chn u tin phi l mng 2, ngy chn th 3 trong thng l :
2 + 28 = 30 0,5 im
Vy ngy 26 thng vo ch nht. 0,5 im
Bi 5:
Gi chiu rng hnh ch nht l a.
Sau khi m thm th chiu rng l
0,5
Vy chiu rng tng thm: =
0,5
Chiu rng tng thm s mt l :
280 : 35 = 8 ( m)
0,5
Suy ra:
0,5
Vy chiu rng ca hnh ch nht( khu vn )l:
8 x 2 = 16 (m )
0,75
Din tch ca khu vn sau khi m thm l:
( 16 + 8 ) x 35 = 840 ( m2)
0,75
p s: 16 m; 840 m2
0,5
(0,25 im)
(0,25 im)
(0,5 im)
(0,5 im)
(0,5 im)
(0,25 im)
(0,25 im)
(0,25 im)
(0,25 im)
(0,25 im)
(0,25 im)
(0,25 im)
(0,25 im)
(0,25 im)
PAGE 11GV Tn N Bch Vn tng hp v gii thiu
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