10:0,25+10:0,125-10:0,2
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\(a)101\times0,75-0,75\)
\(=0,75\times(101-1)\)
\(=0,75\times100=75\)
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`b)10:0,5+4:0,25+8:0,125`
\(=10\times2+4\times4+8\times8\)
\(=5\times4+4\times4+4\times16\)
\(=4\times(5+4+16)\)
\(=4\times25=100\)
\(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)
\(=\left(\dfrac{1}{10}+\dfrac{9}{10}\right)+\left(\dfrac{2}{10}+\dfrac{8}{10}\right)+\left(\dfrac{3}{10}+\dfrac{7}{10}\right)+\left(\dfrac{4}{10}+\dfrac{6}{10}\right)+\dfrac{5}{10}\)
\(=1+1+1+1+\dfrac{5}{10}\)
\(=4+\dfrac{5}{10}\)
\(=\dfrac{45}{10}\)
\(13,25:0,5+13,25:0,25+13,25:0,125+13,25\times6\)
\(=13,25:\dfrac{1}{2}+13,25:\dfrac{1}{4}+13,25:\dfrac{1}{8}+13,25\times6\)
\(=13,25\times2+13,25\times4+13,25\times8+13,25\times6\)
\(=13,25\times\left(2+4+8+6\right)\)
\(=13,25\times20\)
\(=265\)
a)2×4,8× 0,5 +4× 16× 0,25+ 20: 10× 0,5
=(2×0,5)×4,8+(4×0,25)×16+(2×0,5)
= 4,8 + 16 +1
=21,8
b)12,5 × 3,14 ×8 +16 ×0,125 × 1,57
= 0,125×100×3,14×8+16×0,125×1,57
=(0,125×3,14×8+8×2×0,125×1,57)×100
=[0,125×3,14×8+8×0,125×(1,57×2)]×100
=[0,125×3,14×8+8×0,125×3,14]×100
= [(0,125×3,14×8)×2]×100
=6,28×100
=628
Tính thuận tiện:
a, 46 : 24 + 8 : 24
= (46 + 8) : 24
= 54 : 24
= \(\dfrac{9}{4}\)
b, 705 : 45 - 336 : 45
= (705 - 336): 45
= 369 : 45
= \(\dfrac{41}{5}\)
c, 2345 : 12,5 : 8
= 2345 : (12,5 x 8)
= 2345 : 100
= 2,345
A) 0,25 x 37,1 x 40
= ( 0,25 x 40 ) x 37,1
= 10 x 37,1
= 371
B) 612,37 x 8 x 0,125
= 612,37 x ( 8 x 0,125 )
= 612,37 x 1
= 612,37
A) x + 18,7 = 50,5 : 2,5
x + 18,7 = 20,2
x = 20,2 - 18,7
x = 1,5
B) 80 - x = 0,78 x 10
80 - x = 7,8
x = 80 - 7,8
x = 72,2
Tính thuận tiện
a)0,25x37,1x40
=(0,25x40)x37,1
=10x37,1
=371
b)612,37x8x0,125
=612,37x(8x0,125)
=612,37x1
=612,37
Tìm x
a)x+18,7=50,5:2,5
x+18,7=20,2
x =20,2-18,7
x =1,5
b)80-x=0,78x10
80-x=7,8
x=80-7,8
x=72,2
`a)1/10 + 2/10 + 3/10 + 4/10 + 5/10 + 6/10 + 7/10 + 8/10 + 9/10`
`=(1/10+9/10)+(2/10+8/10)+(3/10+7/10)+(4/10+6/10)+5/10`
`=10/10 + 10/10+10/10+10/10+1/2`
`=1+1+1+1+1/2`
`=2+2+1/2`
`=4+1/2`
`=8/2+1/2`
`=9/2`
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`13,25:0,5+13,25:0,25+13,25:0,125+13,25×6`
`=13,25×1/(0,5)+13,25×1/(0,25)+13,25×1/(0,125)+13,25×6`
`=13,25×(1/(0,5)+1/(0,25)+1/(0,125)+6)`
`=13,25×(2+4+8+6)`
`=13,25×20`
`=265`
`#QiN`
25 x 80 + 25 : 0,125 + 25 : 0,1 + 25 : 0,5
= 25 x 80 + 25 x 8 + 25 x 10 + 25 x 2
= 25 x ( 80 + 8 + 10 + 2 )
= 25 x 100
= 2500
25 x 80 + 25 : 0,125 + 25 : 0,1 + 25 : 0,5
= 25 x 80 + 25 x 8 + 25 x 10 + 25 x 2
= 25 x ( 80 + 8 + 10 + 2 )
= 25 x 100
= 2500
3,45 nhân 3+3,45 nhân 2+3,45 nhân 5
=3,45 nhân[3+2+5]
=3,45 nhân 10
=34,5
`34,5 xx 3 + 3,45 : 0,5 + 3,45 : 0,2`
`= 34,5 xx 3 + 3,45 xx (5 + 2)`
`= 34,5 xx 3 + 3,45 xx 7`
`= 3,45 xx 10`
`= 34,5`
10:0,25+10:0,125-10:0,2= 10x(1/0,25+1/0.125-1/0,2)=10 x(4+8-5)=70
10 : 0,25 + 10 : 0,125 - 10 : 0,2
= 10 x 4 + 10 x 8 - 10 - 5
= 10 x ( 4 + 8 - 5 )
= 10 x 7
= 70