Question

(1+3+5+7+…+97+99)-(2+4+6+8+…+96+98)=

Answer 1

1.1-2+3-4+5-6+7.-98+99

=1+(3-2)+(5-4)+.+(99-98)

=1+1+1+1+.+1+1

=50

2.(30-29)+(28-27)+.+(4-3)+(2-1)

=1+1+1+1+.+1+1

=15