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(2+4+6+8+...+100) x (15x3-15x2-15)
=(2+4+6+8+....+100)x(15x(3-2-1))
=(2+4+6+8+...+100)x(15x0)
=(2+4+6+8+...+100)x0
=0
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a) = \(\frac{5\cdot7\cdot8\cdot9\cdot10}{7\cdot8\cdot9\cdot10\cdot11}\)
= \(\frac{5}{11}\) gạch hết các chữ số 7 , 8 , 9 , 10.
b) = \(\frac{3\cdot145+3\cdot55}{6\cdot215+6\cdot85}\)
= \(\frac{3\cdot\left(145+55\right)}{6\cdot\left(215+85\right)}\)
= \(\frac{3\cdot200}{6\cdot300}\)
= \(\frac{1}{3}\)
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1/5 * 2/6 * 3/7 * 4 = 1/5 * 1/3 * 3/7 * 4
= 1/5 * 1/7 * 4
= 1/35 * 4
= 1/140
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2*5*25*8*8*125=(2*5)*(25*4)*(125*8)=10*100*1000=1000000
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2 x 5 + 5 x 7 + 9 x 3
= 5 x ( 2 + 7 ) + 9 x 3
= 5 x 9 + 9 x 3
= 9 x ( 5 + 3 )
= 9 x 8
= 72
2x5+5x9+9x3 15:5+27:5+8:5
=9x5+(2+3) =(15+8+27):5
=9x5+5 =50:5
=9x5+5x1 =10
=5x(9+1) 9+9x3+18:2x6
=5x10 =1x9+9x3+9x6
=50 =9x(1+6+3)
=9x10
=90
19,45:0,5+19,45x8
=19,45x2 +19,45x8
=19,45x(2+8)
=19,45x10
=194,5