Question

1+2+3+4+5+6+......99等于多少

Answer 1

（1+99）×99÷2=100×99÷2=9900÷2=4950

Answer 2

（首项+末项）乘 项数 除以 2

Answer 3

(1+99) *99/2=4950

Answer 4

1+2+3+4+5+6+……+99

=（1+99）+（2+98）+(3+97)+……+(49+51)+50

=100×49+50

=4950

Answer 5

=（1+100)x100÷2-100
=101x50-100
=5050-100
=4950