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\(a)\)\(\left(1989.1990+3978\right)\div\left(1992.1991-3984\right)\)
\(=\)\(\left(1989.1990+1989.2\right)\div\left(1992.1991-1992.2\right)\)
\(=\)\(\left[1989.\left(1990+2\right)\right]\div\left[1992.\left(1991-2\right)\right]\)
\(=\)\(\left(1989.1991\right)\div\left(1992.1989\right)\)
\(=\)\(1\)
\(b)\)\(\left(637.527-189\right)\div\left(526.637+448\right)\)
\(=\)\(\left[637.\left(526-1\right)-189\right]\div\left(526.637-448\right)\)
\(=\)\(\left[637.526+\left(637-198\right)\right]\div\left(637.526-448\right)\)
\(=\)\(\left(636.526+448\right)\div\left(637.526-448\right)\)
\(=\)\(1\)
a) ( 1989 x 1990 + 3978 ) : ( 1992 x 1991 - 3984 )
= 3 962 088 : 3 962 088
= 1
= ( 1989.1990 + 1989.2) : ( 1992.1991 - 1992.2 )
= 1989.(1990 + 2 ) : 1992.( 1991 - 2 )
= 1989.1992 : 1992.1989
\(\Rightarrow\)= 1
a) 86 + 357 + 14 b) 72 + 69 + 128 c) 25.5.4.27.2 d) 28.64 + 28.36
= (86 + 14) + 357 = (72 + 128) + 69 = (25.4).(5.2).27 = 28.(36+64)
= 100 + 357 = 200 + 69 = 100.10.27 = 28.100
= 457 = 269 = 1000.27 = 27000 = 2800
a,86+357+14=[86+14]+357
=100+357
=457
b,72+69+128=[72+128]+69
=200+69
=269
c,25.5.4.27.2=[25.4].[5.2].27
=100.10.27
=1000.27
=27000
d,28.64+28.36=28.[64+36]
=28.100
=2800
\(35x4=\left(25+15\right)x4=100+60\)\(=160\)
\(25x36=25x4x9=100x9=900\)
\(35\times4=140\)
\(25\times36=900\)
\(36\times12=432\)
\(75\times11=825\)
\(67\times101=6767\)
a). 25.5.4.27.2=(25.4).(5.2).27=100.10.27=1000.27=27000
b). 28.64+28.36=28.(64+36)=28.100=2800
(637.527-189):(526.637+448)
= \(\frac{637.527-189}{526.637+448}\)
= \(\frac{637.\left(526+1\right)-189}{526.637+448}\)
= \(\frac{637.526+637-189}{526.637+448}\)
= \(\frac{637.526+448}{526.637+448}\)
= \(1\)
\(\left(1989.1990+3978\right):\left(1992.1991-3984\right)\)
\(=\left(1989.1990+1989.2\right):\left(1992.1991-1992.2\right)\)
\(=\left[1989.\left(1990+2\right)\right]:\left[1992.\left(1991-2\right)\right]\)
\(=\left[1989.1992\right]:\left[1992.1989\right]\)
\(=1\)
\(\left(637.527-189\right):\left(526.637+448\right)\)
\(=\left[637.\left(526+1\right)-189\right]:\left(526.637+448\right)\)
\(=\left[637.526+448\right]:\left(526.637+448\right)\)
\(=1\)