( 112 + 2.28-5.28) : 28

= ( 4.28 + 2.28 - 5.28 ) : 28

= ( 6.28-5.28 ) : 28

= 28 : 28

= 1

(112+2.28-5.28):28 

= 28 : 28 = 1

=(112+(2-5).28):28

=(112+(-84)):28

=28:28

=1

\(\left(112+2\cdot28-5\cdot28\right):28\)

\(=\left(4\cdot28+2\cdot28-5\cdot28\right):28\)

\(=28\cdot\left(4+2-5\right):28\)

\(=1\cdot\left(6-5\right)\)

\(=1\cdot1\)

\(=1\)

Đ/á: 6

         Bài làm :

Ta có :

\(...=\left(9.28+2.28-5.28\right)\div28=28.\left(9+2-5\right)\div28=9+2-5=6\)

(28.9 + 2.28 - 5.28) : 28

=( 9 + 2 - 5) .28 : 28

= 6.(28:28)

= 6

\(\left(28.9-2.28-5.28\right):28\\ =\left[28.\left(9-2-5\right)\right]:28\\ =28.2:28\\ =28:28.2\\ =2\)

\(2^3.3^2.28+2^3.3^5.8\\ =2^3.3^2.2^2.7+2^3.3^5.2^3\\ =2^5.3^2.7+2^6.3^5\\ =2^5.3^2\left(7+2.3^3\right)\\ =32.9\left(7+54\right)\\ =32.9.61=17568\)

\(2^3.3^2.28+2^3.3^5.28\)

=> \(28.(2^3.3^2+2^3.3^5)\)

=> \(28.[3^3(3^2+3^5)]\)

=> \(28.[3^3.252]\)

=> ............( tự tính)

toan lop 3 no con lam dc

Phân số chỉ phần diện tích đất làm lối đi là:

 \(1-\dfrac{1}{6}-\dfrac{3}{4}=\dfrac{12-2-9}{12}=\dfrac{1}{12}\)

Diện tích mảnh đất là:

\(52:\dfrac{1}{12}=52x12=\left(50+2\right)x12=600+24=624\left(m^2\right)\)

a/

31.64+7.30+146.31=31.(64+146)+7.30

=31.210+7.30=6510+210=6720

b/2³.3².28+2³.3⁵.8=2³.(3².28+3⁵.8)

=2³.(9.28+243.8)=8.(252+1944)

=8.2196=17568