a) 72 + 9 + 8 = ( 72 + 8 ) + 9

= 80 + 9

= 89

b)37 + 18 + 3 = ( 37 + 3 ) + 18

= 40 + 18

= 58

c) 48 + 26 + 4 = 48 + (26 + 4)

= 48 + 30

= 78

d)85 + 99 + 1 = 85 + ( 99 + 1 )

= 85 + 100 = 185

e) 67 + 98 + 33 = ( 67 + 33 ) + 98

= 100 + 98 = 198

1) \(373737.73-37.737373\)

\(=37.10101.73-37.73.10101\)

\(=0\)

2) \(19.41414141-41.19191919\)

\(=19.41.1010101-41.19.1010101\)

\(=0\)

3) \(123456.456789456789-456789.123456123456\)

\(=123456.456789.1000001-456789.123456.1000001\)

\(=0\)

4) \(250.12.7\)

\(=250.4.3.7\)

\(=\left(250.4\right).\left(3.7\right)\)

\(=1000.21\)

\(=21000\)

5) \(24.125.9\)

\(=3.8.125.9\)

\(=\left(3.9\right).\left(8.125\right)\)

\(=27.1000\)

\(=27000\)

6) \(125.44.18\)

\(=125.4.11.2.9\)

\(=\left(125.4.2\right).\left(11.9\right)\)

\(=1000.99\)

\(=99000\)

7) \(8.24.6+12.4.52+2.22.24\)

\(=48.24+48.52+48.22\)

\(=48\left(24+52+22\right)\)

\(=48.98\)

\(=48\left(100-2\right)\)

\(=48.100-48.2\)

\(=4800-96\)

\(=4704\)

8) \(18.58.2-9.27.4+12.69.3\)

\(=36.58-36.27+36.69\)

\(=36\left(58-27+69\right)\)

\(=36.100=3600\)

9) \(30.85.3+18.72.5-45.37.2-9.20.10\)

\(=90.85+90.72-90.37-90.20\)

\(=90\left(85+72-37-20\right)\)

\(=90.100=9000\)

a,7429-(3125+4297)

=7407-93103+4297)

=7407-7400

7

b,9/8-(17/7-3/7)+7/8

=(9/8 +7/8)-(17/7-3/7)

=2-2

=0

c,tự làm nhé..

19/37+1-19/37

=(19/37-19/37)+1

=0+1

=1

9/8-(17/7-3/7)+7/8

=(9/8+7/8)-(17/7-3/7)

=2-2

=0

1/2+3/4+1/2

=(1/2+1/2)+3/4

=1+3/4

=7/4

19/37 + 1 - 19/37 = (19/37 - 19/37) + 1 = 1

9/8 - (17/7 - 3/7) + 7/8 = (9/8 + 7/8) - (17/7 - 3/7) = 16/8 - 14/7 = 2 - 2 = 0

1/2 + 3/4 + 1/2 = (1/2 + 1/2) + 3/4 = 1 + 3/4 = 7/4

a, 19/37+1-19/37

= (19/37-19/37)+1

=1

b, 9/8- (17/7-3/7)+7/8

= (9/8+7/8) - (17/7-3/7)

=16/8 - 14/7

= 2 - 2

=0

c, 1/2+3/4+1/2

= (1/2+1/2)+3/4

=1+3/4

=7/4

a) 1-5+7-8+4-1+5-7+8

=(1-1) - (-5+5) -(7-7) -(-8+8) +4

=0

b)=-39+9

=-30

c)=(20-20)-(-4+4)-(8-8)-17+15

=-2

d)= (13-13)-(-98+98)-(91-91)-75

=-75

\(\left(\frac{2}{9}+\frac{7}{9}\right)+\left(\frac{1}{5}+\frac{4}{5}\right)=1+1=2\)\(2\)

\(\frac{19}{37}+1-\frac{19}{37}=\left(\frac{19}{37}-\frac{19}{37}\right)+1=1\)

=2 nha bn mk bấm nhầm

a ) 37 x 27 + 63 x 27 

= ( 37 + 63 ) x 27

= 100 x 27

= 2700

b ) 1 + 2 + 3 + 4 + ... + 97 + 98 + 99

= ( 99 - 1 ) : 1 + 1 

= 99 x ( 99 + 1 ) : 2 

= 4950

c ) 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10

= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + ( 5 + 10 )

= 10 + 10 + 10 + 10 + 15

= 55

37 x 27 x 63 x27

=(37+63)x27

=100 x 27

37 x 27 + 63 x 27

= ( 37 + 63 ) x 27

= 100 x 27

= 2700

1 + 2 + 3 + 4 + ... + 97 + 98 + 99

= ( 1 + 99 ) + ( 2 + 98 ) + .... + ( 51 + 49 ) + 50

= 100 + 100 + ... + 100 + 50   ( có 49 số 100 )

= 100 x 49 + 50

= 4900 + 50

= 4950

1 + 2 + 3 +4 + 5 + 6 +7 + 8 + 9 + 10

= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 10 + 5

= 10 + 10 + 10 + 10 +10 + 5

= 10 x 5 + 5

= 55

cậu ấn máy tính không được à

Phải trình bày rõ ràng chứ

a) \(1-5+7-8+4-1+5-7+8\)

\(=\left(1-1\right)+\left(5-5\right)+\left(7-7\right)+\left(8-8\right)+4\)

\(=0+0+0+0+4\)

\(=4\)

b) \(12-14+9-3-14+9-3+14-19-9-12\)

\(=\left(12-12\right)+\left(9-9\right)+\left(14-14\right)+9-3-3\)

\(=0+0+0+9-6\)

\(=3\)

c) \(20-4+8-17+4-8-20+15\)

\(=\left(20-20\right)+\left(4-4\right)+\left(8-8\right)+\left(-17+4+15\right)\)

\(=0+0+0+2\)

\(=2\)

\(13-98+91-75+98-91-13\)

\(=\left(13-13\right)+\left(98-98\right)+\left(91-91\right)-75\)

\(=0+0+0-75\)

\(=-75\)