简算与计算

6.7*12+6.7*35+6.7*52+6.7
=6.7*12+6.7*35+6.7*52+6.7*1
=6.7*（12+35+52+1）
=6.7*100
=670

1 6.7×12+6.7×35+6.7×52+6.7
===6.7×（12+35+52+1）
===6.7×100
===670
2 9999999×8888888÷6666666
===9×1111111×8×111111÷6÷1111111
===3×1111111×2
===6666666
3 1+2+4+8+16+32+64+128+256
===2^0+2^2+2^3+2^4+2^5+2^6+2^7+2^8(2的次方）
===2^0(1-2^9)/(1-2)
===2^9-1
===512-1
===511
4 321×654÷987÷654×987÷321
===(约去了)1
5 100+99-98-97+96+95-94-93+…+4+3-2-1
===(100+99-98-97)+(96+95-94-93)+(92+91-90-89)+…+4+3-2-1
===(2+2)+(2+2)+(2+2)++…+(2+2)(全部由100÷4个2+2)
===(2+2)×25
===100

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