Question

101−95+91−85+…+31−25+21−15+11−5=?

Answer 1

= (101+91+...+11) - ( 95+85+...+5)

=560 - 500

= 60

Answer 2

tinh theo quy luật.

Answer 3

101−95+91−85+…+31−25+21−15+11−5 ( 20 số )

= 6 + 6 + ......+ 6 + 6 + 6 ( có 10 số )

= 6 x 10

= 60