Question

Tính nhanh:

    21+22+23+24+25+26+27+28+29+30

Answer 1

   21 + 22 + 23 + 24 + 25 + 26 + 27 + 28 + 29 + 30

= (21 + 30) + (22 + 29) + (23 + 28) + (24 + 27) + (25 + 26)

=      51     +      51      +      51      +      51     +      51

=      51 x 5

=      255

Answer 2

=(21+29)+(22+28)+(23+27)+(24+26)+25+30

=50+50+50+50+25+30

=200+25+30

=225+30

=255

Answer 3

Tính nhanh:

    21+22+23+24+25+26+27+28+29+30 

= 50 + 50 + 50 +50 + 25 + 30

= 200 + 25 +30 

=225 + 30 

= 255

Answer 4

21 + 22 + 23 + 24 + 25 + 26 + 27 + 28 + 29 + 30

= ( 21 + 30 ) x 10 : 2

= 255

Answer 5

=(21+30)+(22+29)+(23+28)+(24+27)+(25+26)

=   51     +   51    +    51   +   51     +    51

=51x5

255

Answer 6

21+22+23+24+25+26+27+28+29+30

=(21+30)+(22+29)+(23+28)+(24+27)+(25+26)

=   51       +   51     +    51    +   51    +   51

= 51 x 5

=255

ai k mh mh k lại