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a ) 17 x 4 = ( 15 + 2 ) x 4 = 15 x 4 + 2 x 4 = 60 + 8 = 68
25 x 28 = 25 x ( 20 + 8 ) = 25 x 20 + 25 x 8 = 500 + 200 = 700
b ) 13 x 12 = 13 x ( 10 + 2 ) = 13 x 10 + 13 x 2 = 130 + 26 = 156
53 x 11 = 53 x ( 10 + 1 ) = 53 x 10 + 53 x 1 = 530 + 53 = 583
39 x 101 = 39 x ( 100 + 1 ) = 39 x 100 + 39 x 1 = 3900 + 39 = 3939
a) Ta có:
\(17\times4=\left(15+2\right)\times4=15\times4+2\times4=60+8=68\)
\(25\times28=25\times\left(20+8\right)=25\times20+25\times8=500+200=700\)
b) Ta có:
\(13\times12=13\times\left(10+2\right)=13\times10+13\times2=130+26=156\)
\(53\times11=53\times\left(10+1\right)=53\times10+53\times1=530+53=583\)
\(39\times101=39\times\left(100+1\right)=39\times100+39\times1=3900+39=3939\)
17.4 = 17.(2.2) = (17.2).2 = 34.2 = 68
25.28 = 25.(4.7) = (25.4).7 = 100.7 = 700
13.12 = 13.(10+2) = 13.10 + 13.2
= 130 + 26 = 156
53.11= 53.(10+1) = 53.10 + 53.1
= 530 + 53 = 583
39.101 = 39.(100+1) = 39.100 + 39.1
= 3900 + 39 = 3939
a: =35/17-18/17-9/5+4/5
=1-1=0
b: =-7/19(3/17+8/11-1)
=7/19*18/187=126/3553
c: =26/15-11/15-17/3-6/13
=1-6/13-17/3
=7/13-17/3=-200/39
17x4=17x2x2=(17x2)x2=34x2=68
25.28=25.4.7=(25.4.7)=100.7=100
13.12=13.(10+2)=13.10+13.2=130+26=156
53.11=53.(10+1)=53.10+53.1=530+53=583
39.101=39.(100+1)=39.100+93.1=3900+39=3939
1) 2763 +152 =2915
2) (-7) +(-14) = -21
3) (-35) + (-9) = -44
4) (-5) + (-248) = -253
5) (-23) + 105 = 82
6) 78 + (-123) = -45
7) 23 +(-13) = 10
8) (-23) +13 = -10
9) 26 + (-6) = 20
10) (-75) +50 = -25
11) 80 + (-220) = -140
12) (-23) + (-13) = -36
13) (-26) + (-6) = -32
14) (-75) + (-50) = -125
15) ❏-18❏ + (-12) = -17❏ -12
16)17 + ❏ - 33❏ = 17 -32❏
17) (-20) +❏ - 88❏ = -20 -87❏
18) ❏- 3❏+ ❏5❏ = ❏5❏ -2❏
19)❏-37❏+❏15❏ = ❏15❏ -36❏
20) ❏-37❏+(-❏15❏) = -❏15❏ - 36❏
21) (-❏-32❏) +❏5❏ = ❏5❏ -33❏
22) (-❏-22❏) + (-❏16❏) = -❏16❏ -23❏
23) (-23) +13 +(-17) +57 = 30
24) 14 +6 + (-9) + (-14) = -3
25) (-123 ) +❏-13❏+(-7) = -130-12❏
26) ❏0❏ + ❏45❏ +(-❏-455)❏+❏-796❏ = ❏45❏-❏\(^2\) -1250❏
1+2+3+4+5+6+7+8+9+10=55
11+12+13+14+15+16+17+18+19+20=155
1+2+3+4+5+6+7+8+9+10+11+12+13+14 +15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30-50-53=362
1) 33 + 18 + 22 + 17
= (33 + 17) + (18 + 22)
= 50 + 40 = 90
2) 101 + 778 + 583 + 299 + 17
= (101 + 299) + (583 + 17) + 778
= 400 + 600 + 778
= 1000 + 778 = 1778
3) 25.13.4 + 2.17.50
= 100.13 + 100.17
= 100.(13 + 17)
= 100.30 = 3000
4) 34.50 = 17.2.50 = 17.100 = 1700
5) 24.25 = 24.5.5 = 100.5 = 500
6) 32.125 = 4.8.125 = 4.1000 = 4000
7) 25.9.11.4 = (25.4).(9.11) = 100.99 = 9900
8) 8.14.125.5 = (8.125).(14.5) = 1000.70 = 70000
9) 4.27.25.10 = (4.25).(27.10) = 100.270 = 27000
10) 16.125.23 = 2.8.125.23 = (2.23).(8.125) = 46.1000 = 46000
11) 375 + 693 + 625 + 307
= (375 + 625) + (693 + 307)
= 1000 + 1000 = 2000
12) 238 + 634 + 672
= (238 + 672) + 634
= 910 + 634 = 1544
13) 586 + 47 + 414
= (586 + 414) + 47
= 1000 + 47 = 1047
14) 237 + 301 + 183 + 129
= (237 + 183) + (301 + 129)
= 420 + 430 = 850
15) 123.23 + 123.11 + 123.65 + 123
= 123.(23 + 11 + 65 + 1)
= 123.100 = 12300
Câu 15 bạn ghi thừa 123.11 phải không?
1) 33+18+22+17=(33+17)+(18+22)=50+40=90
2)101+778+583+299+17= (101+299)+ (583+17)+778=400+600+778=1778