Question

小学奥数;10*9-9*8+8*7-7*6+6*5-5*4+4*3-3*2+2*1解题步骤？

10*9-9*8+8*7-7*6+6*5-5*4+4*3-3*2+2*1解题步骤

Answer 1

原式=9×(IO一8)十7×(8一6)十5x(6一4)十3x(4一2)十2×1
=9x2十7X2十5×2十3×2十1×2
=2(1十3十5十7十9)
=2x25
=5O

Answer 2