2:

=1-1+1-1=0

3:

a: =>34*(100+1)/2:a=17

=>a=101

b: =>5/3(x-1/2)=5/4

=>x-1/2=5/4:5/3=3/4

=>x=5/4

1a, \(\dfrac{2005}{2001}\) = 1+\(\dfrac{4}{2001}\); \(\dfrac{2009}{2005}\)=1+\(\dfrac{4}{2005}\)vì\(\dfrac{4}{2001}\)>\(\dfrac{4}{2005}\)nên\(\dfrac{2005}{2001}\)>\(\dfrac{2009}{2005}\)

1b,\(\dfrac{1313}{1515}\)=\(\dfrac{1313:101}{1515:101}\)= \(\dfrac{13}{15}\); \(\dfrac{131313}{151515}\)=\(\dfrac{131313:10101}{151515:10101}\)=\(\dfrac{13}{15}\)

Vậy \(\dfrac{13}{15}\)=\(\dfrac{1313}{1515}\)=\(\dfrac{131313}{151515}\)

a, 30,24 + 30,24 + 30,24 + 30,24 x 7 - 30,24 : 0,1

= 30,24 x 3 + 30,24 x 7 - 30,24 : 0,1

= 30,24 x 10 - 30,24 : 0,1

= 30,24 x 10 - 30,24 x 10

= 0

b, 2 giờ 30 phút x 8 + 2,5 giờ x 3 - 150 phút

= 2,5 giờ x 8 + 2,5 giờ x 3 - 150 phút

= 2,5 giờ x 8 + 2,5 giờ x 3 - 2,5 giờ

= 2,5 giờ x 10

= 25 giờ

c, 1/2 : 0,5 - 1/4 : 0,25 + 1/8 : 0,125 - 1/10 : 0,1

= 1/2 x 2 + 1/4 x 4 + 1/8 x 8 - 1/10 x 10

= 1 + 1 + 1 - 1

= 2 

=30,24(1+1+1+7-0,1)

=30,24x9,9

=299,376

\(x\) + \(x\): 0,25 + \(x\) : 0,5 + \(x\) : 0,125 = 40

\(x\) \(\times\) 1+ \(x\) \(\times\) 4 + \(x\) \(\times\) 2 + \(x\times\) 8 = 40

\(x\) \(\times\) ( 1 + 4 + 2 + 8) = 40

\(x\) \(\times\) 15 = 40

\(x\)          = 40 : 15

\(x\)          = \(\dfrac{8}{3}\)

a) 128,5 : 0,5 + 128,5 x 3 + 128,5 : 0,25 + 128,5

=128,5 x 2 +128,5 x 3 +128,5 x 4 +128,5 x 1

=128,5 x ( 2 + 3 + 4 + 1 )

=128,5 x 10

=1285

b) 17,2 x 9,55 + 9,45 x 17,2 + 17,2

= 17,2 x 9,55 + 9,45 x 17,2 + 17,2 x 1

=17,2 x ( 9,55 +9,45 + 1 )

=17,2 x 20

=344

c) 6,45 : 0,2 + 6,45 : 0,25 + 6,45 - 6,45 : 0,1

=6,45 x 5 + 6,45 x 4 +6,45 x 1 + 6,45 x 10

=6,45 x (5 +4+1+10)

=6,45x20

=129

d) 1/2 : 0,5 - 1/4 : 0,25 + 1/8 : 0,125 - 1/10 : 0,1

=0,5;0,5-0,25:0,25+0,125:0,125-0,1:0,1

=1-1+1-1

=0

Có ai biết làm phép tính 24,48/0,25

\(x\times4+x\times2+x\times10+x+x\times100=23,4\)

\(x\times\left(4+2+10+100\right)=23,4\\ x\times116=23,4\\ x=\dfrac{23,4}{116}\approx0,2\)

a: \(2\cdot4\cdot8\cdot0,5\cdot0,125\cdot0,25\cdot\left(0,4321+0,5679\right)\)

\(=\left(2\cdot0,5\right)\cdot\left(4\cdot0,25\right)\cdot\left(8\cdot0,125\right)\cdot1\)

\(=1\cdot1\cdot1\cdot1=1\)

b: \(3,7\cdot3,8+8,3\cdot3,7-0,4\cdot3,7\cdot5\)

\(=3.7\left(3,8+8,3\right)-3,7\cdot2\)

\(=3,7\cdot12,1-3,7\cdot2\)

\(=3,7\left(12,1-2\right)=3,7\cdot10,1=37,37\)

c: \(0,51:0,1+0,57:1,9+0,49:0,1-0,3\)

\(=0,51\cdot10+0,49\cdot10+0,57:1,9-0,3\)

\(=10\left(0,51+0,49\right)+0,3-0,3\)

\(=10\cdot1=10\)