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a)
160 : (4 × 8) = 160 : 32 = 5
160 : 4 : 8 = 40 : 8 = 5
Vậy 160 : (4 × 8) = 160 : 4 : 8.
96 : (3 × 8) = 96 : 24 = 4
96 : 3 : 8 = 32 : 8 = 4
Vậy 96 : (3 × 8) = 96 : 3 : 8.
105 : (5 × 7) = 105 : 35 = 3
105 : 5 : 7 = 21 : 7 = 3
Vậy 105 : (5 × 7) = 105 : 5 : 7.
Nhận xét: a : (b × c) = a : b : c
b)
270 : (9 × 6) = 270 : 9 : 6 = 30 : 6 = 5
420 : (7 × 3) = 420 : 7 : 3 = 60 : 3 = 20
144 : (2 × 8) = 144 : 2 : 8 = 72 : 8 = 9
Ta có:
a) ( 45 – 5 x 9 ) x 1 x 2 x 3 x 4 x 5 x 6 x 7
= (45 – 45) x 1 x 2 x 3 x 4 x 5 x 6 x 7
= 0 x 1 x 2 x 3 x 4 x 5 x 6 x 7
= 0
b) (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10) x (72 – 8 x 8 – 8)
= (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10) x (72 – 64 – 8)
= (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10) x 0
= 0
c) (36 – 4 x 9) : (3 x 5 x 7 x 9 x 11)
= (36 – 36) : (3 x 5 x 7 x 9 x 11)
= 0 : (3 x 5 x 7 x 9 x 11)
= 0
d) (27 – 3 x 9) : 9 x 1 x 3 x 5 x 7
= (27 – 27) : 9 x 1 x 3 x 5 x 7
= 0 : 9 x 1 x 3 x 5 x 7
=0
a) ( 45 – 5 x 9 ) x 1 x 2 x 3 x 4 x 5 x 6 x 7
= 0 x 1 x 2 x 3 x 4 x 5 x 6 x 7
b) (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10) x (72 – 8 x 8 – 8)
= (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10) x 0
c) (36 – 4 x 9) : (3 x 5 x 7 x 9 x 11)
= 0 : (3 x 5 x 7 x 9 x 11)
d) (27 – 3 x 9) : 9 x 1 x 3 x 5 x 7
= 0 : 9 x 1 x 3 x 5 x 7 Nếu đúng thì k cho mình nhé bạn!
\(a,\dfrac{4}{5}+\dfrac{2}{7}=\dfrac{28}{35}+\dfrac{10}{35}=\dfrac{38}{35}.\)
\(b,2-\dfrac{8}{9}=\dfrac{18}{9}-\dfrac{8}{9}=\dfrac{10}{9}.\)
\(c,\dfrac{5}{8}\times3=\dfrac{5\times3}{8}=\dfrac{15}{8}.\)
\(d,5:\dfrac{6}{21}=5\times\dfrac{21}{6}=\dfrac{5\times21}{6}=\dfrac{105}{6}=\dfrac{35}{2}.\)
\(đ,\dfrac{3}{5}\times\dfrac{4}{5}\times\dfrac{6}{7}=\dfrac{3\times4\times6}{5\times5\times7}=\dfrac{72}{175}.\)
\(a,\dfrac{4}{5}+\dfrac{2}{7}=\dfrac{28}{35}+\dfrac{10}{35}=\dfrac{38}{35}\)
\(b,2-\dfrac{8}{9}=\dfrac{18}{9}-\dfrac{8}{9}=\dfrac{10}{9}\)
\(c,\dfrac{5}{8}\times3=\dfrac{5\times3}{8\times1}=\dfrac{15}{8}\)
\(d,\dfrac{3}{5}\times\dfrac{4}{5}\times\dfrac{6}{7}=\dfrac{3\times4\times6}{5\times5\times7}=\dfrac{72}{175}\)
Bài 1: Tính
a, 1/2 x 2/3 x 3/4 = 1/4
b, 7/8 x 8/9 x 9/10 = 7/10
c, 5/14 x 7/15 x 28/7 = 2/3
d, 2 x 1/2 x 3 x 1/3 x 4 x 1/4 x 5 x 1/5 = 1
Bài 2: Tính
a, 7/20 - ( 5/8 - 3/5 ) = 7/20 - 1/40 = 14/40 - 1/40 = 13/40
b, 5/6 + ( 5/9 - 1/4 ) = 5/6 + 11/36 = 30/36 + 11/36 = 41/36
c, 9/10 - ( 2/5 + 3/10 ) + 7/20 = 9/10 - 7/10 + 7/20 = 2/10 + 7/20 = 4/20 + 7/20 = 11/20.
Bài 3: Tìm x:
a, 1/2 + x = 5/6
x = 5/6 - 1/2
x = 1/3
b, 5/6 - x = 1/3
x = 5/6 - 1/3
x = 1/2
c, x - 1/mấy vậy bạn
d, 1/3 x x = 1/6
x = 1/6 : 1/3
x = 1/2
bài 1
a)\(=\dfrac{16}{40}+\dfrac{15}{40}=\dfrac{31}{40}\)
b)\(=\dfrac{7}{6}-\dfrac{4}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)
c)\(=\dfrac{30}{9}=\dfrac{10}{3}\)
d)\(=\dfrac{8}{5}\times\dfrac{7}{4}=\dfrac{56}{20}=\dfrac{14}{5}\)
Bài 1:
a: x+1/2=5/6
nên x=5/6-1/2=1/3
b: x+1/4=3/4
nên x=3/4-1/4=2/4=1/2
c: x+3/10=1/2
nên x=1/2-3/10=5/10-3/10=1/5
d: x+1/4=3/8
nên x=3/8-1/4=3/8-2/8=1/8
a, (6/11+5/11)x3/17
c1:=1x3/17
=3/17
c2:=6/11x3/17+5/11x3/17
=18/197+15/187
=33/187
=3/17
b,3/5x7/9-3/5x2/9
c1:=21/45-6/45
=15/45
=1/3
c2:=3/5x(7/9-2/9)
=3/5x5/9
=1/3
c,( 6/7-4/7):2/5
c1:=2/7:2/5
=2/7x5/2
=5/7
c2,6/7:2/5-4/7:2/5
=6/7x5/2-4/7x5/2
=15/7-10/7
=5/7
d,8/15:2/11+7/15:2/11
c1:=(8/15+7/15):2/11
=1x11/2
=11/2
c2:=8/15x11/2+7/15x11/2
=88/30+77/30
=165/30
=11/2
a) (\(\frac{6}{11}\) + \(\frac{5}{11}\)) x \(\frac{3}{17}\)= \(\frac{11}{11}\) x \(\frac{3}{17}\)= \(1\) x\(\frac{3}{17}\)= \(\frac{3}{17}\)
b) \(\frac{3}{5}\)x\(\frac{7}{9}\)- \(\frac{3}{5}\)x \(\frac{2}{9}\) = \(\frac{3}{5}\)x (\(\frac{7}{9}\)- \(\frac{2}{9}\))= \(\frac{3}{5}\) x \(\frac{5}{9}\)= \(\frac{3}{9}\)
c) (\(\frac{6}{7}\)- \(\frac{4}{7}\)) : \(\frac{2}{5}\)= \(\frac{2}{7}\) x \(\frac{5}{2}\)= \(\frac{5}{7}\)
d) \(\frac{8}{15}\) : \(\frac{2}{11}\) + \(\frac{7}{15}\): \(\frac{2}{11}\)= ( \(\frac{8}{15}\)+ \(\frac{7}{15}\)) x \(\frac{11}{2}\)= 1 x \(\frac{11}{2}\)= \(\frac{11}{2}\)
Chúc học tốt nha!
\(a,x=\dfrac{4}{5}\times\dfrac{1}{3}=\dfrac{4}{15}\)
\(b,x=\dfrac{7}{9}\times\dfrac{3}{5}=\dfrac{7}{15}\)
\(c,x=\dfrac{7}{6}\times\dfrac{4}{3}=\dfrac{14}{9}\\ d,x=\dfrac{9}{7}\times\dfrac{8}{4}=\dfrac{18}{7}\)
Đáp án B