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65 x 42 - 130 x 21 + 2013
= 2730 - 2730 + 2013
= 0 + 2013
= 2013
học tốt!!!
\(=65\cdot42-65\cdot2\cdot21+2013\)
\(=65\cdot42-65\cdot42+2013\)
\(=2013\)
\(=\dfrac{21}{11}\cdot\dfrac{22}{17}\cdot\dfrac{34}{42}=\dfrac{1}{2}\cdot2\cdot2=2\)
\(21\times35+42\times31+63\)
\(=21\left(35+31\times2+3\right)\)
\(=21\times100\)
\(=2100\)
a) \(21\times35+42\times31+63\)
\(=21\times35+21\times2\times31+21\times3\)
\(=21\times35+21\times62+21\times3\)
\(=21\times\left(35+62+3\right)\)
\(=21\times100\)
\(=2100\)
_Chúc bạn học tốt_
1998 x 497 + 1998 x1 + 1998 x1 + 1998 x1
= 1998 x (497 +1 + 1 + 1 )
=1998 x 500
= 999000
1998 x 497 + 1998 + 1998 + 1998
= 1998 x 497 + 1998 x 3
= 1998 x ( 497 + 3 )
= 1998 x 500
= 999000
a, 42x(54+17):71
=42x71:71=42
b, 123x(154-65):89
=123x89:89=123
c,324x(6+4):324
=324x10:324=10x324:324=10
\(a)\left(42\times54+17\times42\right):71\)
\(=42\times54+17\times42:71\)
\(=42\times\left(54+17\right):71\)
\(=42\times71:71\)
\(=42\)
\(b)\left(123\times154-65\times123\right):89\)
\(=123\times154-65\times123:89\)
\(=123\times\left(154-65\right):89\)
\(=123\times89:89\)
\(=123\)
\(c)\left(324\times6+4\times324\right):\left(162\times2\right)\)
\(=324\times6+4\times324:324\)
\(=324\times\left(6+4\right):324\)
\(=324\times10:324\)
\(=3240:324\)
\(=10\)
a) 6625 + 3525 - 25 d) 35 x 34 + 35 x 86 + 65 x 75 + 65 x 45
= 6625 + ( 3525 -25) = 35 x (34 + 86 ) + 65 x (75 + 45 )
= 6625 + 3500 = 35 x 120 + 65 x 120
= 10 125 = 120 x ( 35 + 65 )
= 120 x 100
= 12 000
a) 6625 + 3525 - 25
=10125
b) 58 x 42 + 32 x 8 + 5 x 16
= 2436 + 256 + 80
= 2772
c) (4243 + 4357 + 43) - 360 : 4
= 8643 - 360: 4
= 8642 - 90
= 8552
d) 35 x 34 + 35 x 86 + 65 x 75 + 65 x 45
= (34 +86) x 35 + (75 + 45) x 65
= 120 x 35 + 120 x 65
= 120 x (35+65)
= 120 x 100
= 12000
65x42-130x21+1998
=65x (2x21)-130x21+1998
=(65x2)x21-130x21+1998
=130x21-130x21+1998
=0+1998
=1998