3.8*5.4+7.2*6.2+1.8*3.8簡便計算

3.8*5.4+7.2*6.2+1.8*3.8簡便計算


=3.8×5.4+1.8×3.8+7.2×6.2
=3.8×(5.4+1.8)+7.2×6.2
=3.8×7.2+7.2×6.2
=(3.8+6.2)×7.2
=10×7.2
=72



4.6-2.8+6.4-7.2能簡便運算嗎?


1



1+2+3+4+5+6+7+8…+100怎麼算.記得有個簡便辦法.


1+2+3+4+5+6+7+8…+100
=(0+100)+(1+99)+(2+98)+……+(48+52)+(49+51)+50
=100×50+50
=101×50
=5050.