5000-1-2-3-4-...-40数学题巧算
问题描述:
5000-1-2-3-4-...-40数学题
巧算
答
5000-1-2-3-4-...-40
=5000-(1+2+3+4+...+40)
=5000-(1+40)*40/2
=5000-820
=4180
答
=5000-(1+2+3+4+……40)
=5000-[(1+40)*40/2]
=5000-(41*20)
=5000-820
=4180