5x273x45/65:(55x24/104x26x34/64)
tính nhanh
dấu / là phần nha
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a) 19.64+79.34=19.2.32+38.2.68
=38.32+38.68
= 38.(32+68)= 38.100
= 3800
b)35.12+65.13= 35.12+65.(12+1)
= (35+65).12
= 100.12
=1200
a) 6 + 2 x 64 x 3 + 4 x 36
= 6 + 6 x 64 + 4 x 6 x 6
= 6 + 6 x 64 + 6 x 24
= 6 x (1 + 64 + 24)
= 6 x 89
= 534
b) 4 + 6 + 12 + ... + 2008 + 2012
= 2 x (2 + 3 + 4 + ... + 1004 + 1005)
= 2 x (2 + 1005) x 1004 : 2
= 1007 x 1004
= 1011028
(18+38+16*76-1)=(36*19+64*20-65)-x
=>(18+38+1216-1)=(684+1280-65)-x
=>1271=1899-x
=>1899-x=1271
x = 1899-1271
x=628
vậy x= 628
( 18 + 38 + 1216 - 1) = ( 684 +1280 - 65) - x
( 56 + 1216 - 1) = ( 1964 - 65) - x
1271 = 1899 - x
x = 1899 - 1271
x = 628
Bài 1 : Tính nhanh :
a) 19 . 64 + 76 .34
= 38 . 32 + 38 . 68
= 38 . (32 + 68)
= 38 .100
= 3800
b) 35 . 12 + 65 . 13
= 35 . 12 + 65 . (12 + 1)
= 35 . 12 + 65 . 12 + 65
= 12 . (35 + 65) + 65
= 1200 + 65
= 1265.
Bài 2 :
a)
A = 1998 . 1998
=1998 . 1996 + 1998 . 2
B = 1996 . 2000
=1998 . 1996 + 1996 . 2
Vì 1998 . 2 >1996 . 2
=>A > B
b)
A= 2000 . 2000
= 1990 . 2000 + 2000 . 10
B = 1990 . 2010
=1990 . 2000 + 1990 . 10
Vì 2000 . 10 > 1990 . 10
=>A > B
a,19.64+76.34 b,35.12+63.13
TẤT CẢ CÁC SỐ CỦA A ĐỀU LỚN HƠN MỌI SỐ CỦA B NÊN A>B
Bài làm :
\(a,35.34+35.38+65.75+65.45\)
\(=35.\left(34+38\right)+65.\left(74+45\right)\)
\(=35.72+65.120\)
\(=2520+780\)
\(=10320\)
\(b,39.8+60.2+21.8\)
\(=\left(39+21\right).8+60.2\)
\(=60.8+60.2\)
\(=60.\left(8+2\right)\)
\(=60.10=600\)
\(c,36.28+36.82+64.69+64.4\)
\(=36.\left(28+82\right)+64.\left(69+4\right)\)
\(=36.110+64.73\)
\(=3960+4672\)
\(=8632\)
\(d,123.1001\)
\(=123123\)
Học tốt
\(\frac{12}{42}=\frac{2}{7}\)
\(\frac{50}{75}=\frac{2}{3}\)
\(\frac{48}{54}=\frac{8}{9}\)
\(\frac{72}{90}=\frac{4}{5}\)
\(A=\frac{2}{3}+\frac{1}{3}+\frac{1}{15}+\frac{1}{75}+\frac{1}{375}+\frac{1}{1875}\)
\(A=\left(\frac{2}{3}+\frac{1}{3}\right)+\frac{1}{15}+\frac{1}{75}+\frac{1}{375}+\frac{1}{1875}\)
\(A=1+\left(\frac{5}{75}+\frac{1}{75}\right)+\frac{1}{375}+\frac{1}{1875}\)
\(A=1+\frac{6}{75}+\frac{1}{375}+\frac{1}{1875}\)
\(A=1+\left(\frac{150}{1875}+\frac{1}{1875}\right)+\frac{1}{375}\)
\(A=1+\frac{151}{1875}+\frac{1}{375}\)
\(A=1+\left(\frac{151}{1875}+\frac{5}{1875}\right)\)
\(A=1+\frac{156}{1875}\)
\(A=\frac{1875}{1875}+\frac{156}{1875}\)
\(A=\frac{677}{625}\)
\(A=\frac{2}{3}+\frac{1}{3}+\frac{1}{15}+\frac{1}{75}+\frac{1}{375}+\frac{1}{1875}\)
\(\Leftrightarrow A=\left(\frac{2}{3}+\frac{1}{3}\right)+\left(\frac{1}{15}+\frac{1}{75}\right)+\left(\frac{1}{375}+\frac{1}{1875}\right)\)
\(\Leftrightarrow A=1+\left(\frac{5}{75}+\frac{1}{75}\right)+\left(\frac{5}{1875}+\frac{1}{1875}\right)\)
\(\Leftrightarrow A=1+\frac{6}{75}+\frac{6}{1875}\)
\(\Leftrightarrow A=1+\frac{2}{25}+\frac{2}{625}\)
\(\Leftrightarrow A=1+\left(\frac{2}{25}+\frac{2}{625}\right)\)
\(\Leftrightarrow A=1+\left(\frac{50}{625}+\frac{2}{625}\right)\)
\(\Leftrightarrow A=1+\frac{52}{625}\)
\(\Leftrightarrow A=\frac{677}{625}\)