a: =20x71=1420

Tính bằng cách thuận tiện nhất :

a) 3254 + 146 + 1698

= ( 3254 + 146 ) + 1698

= 3400 + 1698 

= 5098

b) 467 + 999 + 9533

= ( 467 + 9533 ) + 999

= 10000 + 999

= 10999

c) 789 + 285 + 15

= 789 + ( 285 + 15 )

= 789 + 300

= 1089

Tính bằng cách thuận tiện nhất:

a)3254+146+1698

= (3254+146)+1698

= 3400+1698

= 5098

b)467+999+9533

= 467+9533+999

= (467+9533)+999

= 10999+999

=11998

c)789+285+15

= 789+(285+15)

= 789+300

=1089

Tính bằng cách thuận tiện nhất :

a) 3254 + 146 + 1698

= ( 3254 + 146 ) + 1698

= 3400 + 1698 

= 5098

b) 467 + 999 + 9533

= ( 467 + 9533 ) + 999

= 10000 + 999

= 10999

c) 789 + 285 + 15

= 789 + ( 285 + 15 )

= 789 + 300

= 1089

(36 + 54) × 7 + 7 × 9 + 7

= 90 × 7 + 7 × 9 + 7

= (90 + 9 + 1 ) × 7

= 100 × 7

= 700

A = 700

24 x 55 + 12 x 88 + 24

= ( 24 x 55 ) + ( 12 x 88 ) + 24

= 1320 + 1056 + 24

= 2376 + 24

= 2400

_HT_

\(24\cdot55+12\cdot88+24\)

\(\Leftrightarrow\left(24\cdot55\right)+\left(24\cdot88:2\right)+24\)

\(\Rightarrow\left(24+55\right)+\left(24\cdot44\right)+24\)

\(\Leftrightarrow24\left(55+44+1\right)\)

\(\Leftrightarrow24\cdot100\)

\(\Leftrightarrow2400\)

=(12+88) +(34+46)*2+(55+65)=100+2*80+120=100+160+120=380

kết quả là 380

12 + 34 + 88 + 46 + 55 + 34 + 65 + 46

= (12 + 88) + (34 + 46) + ( 55 + 65) + ( 34 + 46)
= 100 + 80 + 120 + 80

= 380

`a,`

`34,67+5,42+4,58`

`= 34,67+(5,42+4,58)=34,67+10=44,67`

`b,`

`15,27 \times 2 \times 0,5`

`= 15,27 \times (2 \times 0,5)`

`= 15,27 \times 1=15,27`

`c,`

`45,28 \times 45 + 45,28 \times 55`

`= 45,28 \times (45+55)`

`= 45,28 \times 100=4528`

a.

34,67 + 5,42 + 4,58

= (34,67 + 5,42) + 4,58= 40,09 + 4,58 = 44,67 

b. 15,27 x 2 x 0.5

= (15,27 x 2) x 0.5 = 30,54 x 0,5 = 15,27

c. 45,28  x45 + 45,28 x 55

=  45,28 x (45 + 55)

= 45,28 x 100 = 4528

a.\(\dfrac{18}{15}+\dfrac{7}{15}+\dfrac{12}{15}=\dfrac{18+7+12}{15}=\dfrac{37}{15}\)

b.\(\dfrac{9}{7}+\dfrac{8}{7}+\dfrac{11}{7}=\dfrac{9+8+11}{7}=\dfrac{28}{7}=4\)

1.a,=(54+45+1).113

=100.113

=11300

b,=(3/7+8/14)+(4/9+10/18)

=1+1

=2

2.a,=13/10+1/3

=49/30

b,=12/9.(1/12+1/6)

=12/9.1/4

=1/3

c,=3/4.3/2

=9/8

d,=3/2-1/3

=7/6

1:tính bằng cách thuận tiện nhất:

a)54 x 113 + 45 x 113 + 113

= 54 x 113 + 45 x 113 + 113x1

=113 x(54+45+1)

= 113x100

=1300

 b)3/7 + 4/9 + 8/14 + 10/18

=(3/7+8/14)+(4/9+10/18)

=    1           + 1

=2

`a)75<77`

`=>1/75>1/77`

`=>37/75>37/77>35/77`

`b)7779>7569`

`=>1/7779<1/7569`

`=>3734/7569>3734/7779>2099/7779`

\(\sqrt{Ai}giúpmkvớiak\)