Question

Làm bài tập về nhà:

1.Tính nhanh

A, 72 + 137 + 28

B, 347 + 418 + 123 + 12

C, 38 x 63 + 37 x 38

D, 1 + 2 + 3 + …. + 20

 

Answer 1

a ) 72 + 137 + 28 

  =  ( 72 + 28 ) + 137

    =  100 + 137 = 237

b ) 347 + 418 + 123 + 12

=  ( 347 + 123 ) + ( 428 + 12 )

=   470  +  440

 =   910

c ) 38 x 63 + 37 x 38 

   =  38 x ( 63 + 37 ) 

  =   38  x 100

  =   3800

d)  1 + 2 + 3 + ... + 20

=   ( 20 + 1 ) + ( 19 + 2 ) + ... + ( 11 + 10

=  21 x 10

=210 

Answer 2

a) 72+137+28

=(72+28)+137

= 100 + 137

= 237

b) 347+418+123 + 12

= ( 347+123) + (418+12)

= 370 + 430

= 800

c) 38 x 63 + 37 x 38

= 38 x ( 63+37)

= 38 x 100

= 3800

d) 1+2+3+...+20

= ( 1+20) x 20 : 2

= ( 1+20) x ( 20 :2)

= (1+20) x 10

= 21 x 10

= 210

Answer 3

a, 72 + 137 + 28

= ( 72 + 28 ) + 137

=     100         + 137

=            237

b, 347 + 418 + 123 + 12

= ( 347 + 123 ) + ( 418 + 12 )

=        470          +      430

=                900

c, 38 x 63 + 37 x 38

= 38 x ( 63 + 37 )

= 38 x       100

=     3800

d, 1 + 2 + 3 + .... + 20

= ( 20 + 1 ) x ( 20 : 2 )

=       21      x        10

=            210

Answer 4

a) 72 + 137 +28 

= ( 72 + 38 ) + 137

= 100 + 137

=237

b) 347 + 418+  123+ 12

= ( 347 + 123 ) + ( 418 + 12 )

= 470 + 430 = 900

c) 38 x 63 + 37 x 38

= 38 x ( 63 + 37 )

= 38 x 100 = 3800

d) 1 + 2 + 3 ... + 20

=( 20 + 1 ) x ( 20 : 2 )

= 21 x 10

= 210

Answer 5

A,72 + 137 + 28

=( 72+28) + 137

= 100 + 137

= 237

B,347 + 418 + 123 + 12

= ( 347 + 123 ) + ( 418 + 12 )

=  470 + 430 

= 900

C, 38 . 63 + 37 . 38

= 38 . ( 63 + 37 )

= 38 . 100

= 3800

D, 1+2+3...+20

= ( 20 + 1 ) . ( 20 : 2 )

= 21 . 10

= 210

Hok tốt!!!

Answer 6

\(a,72+137+28\)

  \(=\left(72+28\right)+137\)

  \(=100+137\)

  \(=237\)

\(b,347+418+123+12\)

\(=\left(347+123\right)+\left(418+12\right)\)

\(=470+430\)

\(=900\)

\(c,38\times63+37\times38\)

\(=38.\left(63+37\right)\)

\(=38.100=3800\)

\(d,1+2+3+...+20\)

\(=\left(1+20\right)\times\left(20:2\right)\)

\(=21\times10=2100\)