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a, \(\frac{5}{11}\times\frac{7}{25}+\frac{15}{11}\times\frac{1}{5}\)
\(=\frac{5}{11}\times\frac{7}{25}+\frac{5}{11}\times\frac{3}{5}\)
\(=\frac{5}{11}\times\left(\frac{7}{25}+\frac{3}{5}\right)\)
\(=\frac{5}{11}\times\frac{22}{25}\)
\(=\frac{2}{5}\)
b, \(\frac{3}{7}\times\frac{25}{19}-\frac{1}{7}\times\frac{18}{19}\)
\(=\frac{1}{7}\times\frac{75}{19}-\frac{1}{7}\times\frac{18}{19}\)
\(=\frac{1}{7}\times\left(\frac{75}{19}-\frac{18}{19}\right)\)
\(=\frac{1}{7}\times3\)
\(=\frac{3}{7}\)
\(\frac{5}{3}\)x 2 + x : \(\frac{4}{3}\)= \(\frac{29}{7}\)
\(\frac{10}{3}\)+ x : \(\frac{4}{3}\)= \(\frac{29}{7}\)
x : \(\frac{4}{3}\)= \(\frac{29}{7}\)- \(\frac{10}{3}\)
x = \(\frac{17}{21}\)x \(\frac{4}{3}\)
x = \(\frac{68}{63}\)
\(\frac{10}{3}+\frac{x.3}{4}=\frac{29}{7}\)
\(\frac{3x}{4}=\frac{29}{7}-\frac{10}{3}=\frac{17}{21}\)
\(x=\frac{68}{63}\)
b, 3/5 + 4/7 + 2/8 + 10/25 + 9/21 + 28/16
= 3/5 + 4/7 + 2/8 + 2/5 + 3/7 + 14/8
= (3/5 + 2/5) + ( 4/7 + 3/7) + ( 2/8 + 14/8)
= 1 + 1 + 7/4
= 2 + 7/4 = 15/4
c , 8/7 + 7/6 + 5/8 + 10/12 + 24/28 + 6/16
= c , 8/7 + 7/6 + 5/8 + 5/6 + 6/7 + 1/2
= (8/7 + 6/7) + (7/6 + 5/6) + 5/8 + 1/2
= 14/7 + 12/6 + 5/8 + 1/2
= 2 + 2 + 5/8 + 1/2
= 4 + 9/8 = 41/8
Tính bằng 2 cách :
a). 234 x 25 + 234 x 75
C1: \(234\times25+234\times75\)
\(=5850+17550\)
\(=23400\)
C2: \(234\times25+234\times75\)
\(=234\times\left(25+75\right)\)
\(=234\times100\)
\(=23400\)
b). 765 x 123 - 755 x 23
C1: \(765\times123-765\times23\)
\(=94095-17595\)
\(=76500\)
C2: \(765\times123-765\times23\)
\(=765\times\left(123-23\right)\)
\(=765\times100\)
\(=76500\)
=> Bạn xem lại đề ạ!
c). 476 x ( 45 + 55 )
C1: \(476\times\left(45+55\right)\)
\(=476\times100\)
\(=47600\)
C2: \(476\times\left(45+55\right)\)
\(=476\times45+476\times55\)
\(=21420+26180\)
\(=47600\)
d). 2415 : 5 : 5
=> Xem lại đề ạ
e). ( 76 x 28 ) : 7
C1: \(\left(76\times28\right)\div7\)
\(=2128\div7\)
\(=304\)
C2: \(\left(76\times28\right)\div7\)
\(=76\times\left(28\div7\right)\)
\(=76\times4\)
\(=304\)
g). ( 175 + 29070 ) : 5
C1: \(\left(175+29070\right)\div5\)
\(=29245\div5\)
\(=5849\)
C2: \(\left(175+29070\right)\div5\)
\(=175\div5+29070\div5\)
\(=35+5814\)
\(=5849\)
h). ( 3224 - 1236 ) : 4
C1: \(\left(3224-1236\right)\div4\)
\(=1988\div4\)
\(=497\)
C2: \(\left(3224-1236\right)\div4\)
\(=3224\div4-1236\div4\)
\(=806-309\)
\(=497\)
Bài 1
( 4+ 36)+(8+32)+(12+28)+(16+24)+20
= 40 + 40+40 +40 +20 = 40 x 4 + 20 = 180
Bài 2
a.25 + x +43 =156
25+x = 156 - 43
25 + x = 113
x = 113 - 25
x = 88
b.124 - x +14 =87
124 -x =87 -14
124 - x = 73
x =124 - 73
x =51
Bài 1
=(4+36)+(8+32)+(12+28)+(16+24)+20
=40+40+40+40+20
=180
Bài2
a)25+x+43=156
25+x =156-43
25+x =113
x =113-25
x =88
b)
124-x+14=87
124-x =87-14
124-x =73
x =124-73
x =51