Số số hạng của dãy trên là: (30-20):1+1 = 11 (số)
Tổng trên là: (30+20) x 11:2 = 275
Đáp số: 275
=(20+30)+...(24+26)+25
=50+50+50+50+25
=50x4+25
=225
20+21+22+23+24+25+26+27+28+29+30
=(20+30)+(21+29)+(22+28)+(23+27)+(24+26)+25
=50+50+50+50+50+25
=250+25
=275
Ủng hộ mk nkoa!^_^
=(20 + 30 ) + (21 + 29 ) + ( 22 + 28 ) + (23 + 27 ) + (24 + 26 ) + 25
=50 + 50 + 50 + 50 + 25
= 225
20 + 21 + 22+ 23 + 24+ 25 + 26 + 27+ 28 + 29 +30=50+50+50+50+50+25=275
20 + 21 + 22+ 23 + 24+ 25 + 26 + 27+ 28 + 29 +30
= (20 + 30) + ( 21 + 29) + ( 22 + 28) + ( 23 + 27) + ( 24 + 26 )+ 25
= 50 +50 + 50 + 50 + 50 + 25
= 250 + 25
= 275
20 + 21 + 22+ 23 + 24+ 25 + 26 + 27+ 28 + 29 +30=
(20+30)+(21+29)+(22+28)+(23+27)+(24+26)+25=
50+50+50+50+50+25=
50x5+25=275
nhớ k mình nha!
20 + 21 + 22 + 23 + 24 + 25 + 26 + 27 + 28 + 29 + 30
= (20 + 30) + (21 + 29) + (22 + 28) + (23 + 27) + (24 + 26) + 25
= 50 + 50 + 50 + 50 + 50 + 25
= 50 x 5 + 25
= 250 + 25
= 275
k nha sakura !!!
\(20+21+22+23+24+25+26+27+28+29+30\)
\(=\left(20+30\right)+\left(21+29\right)+\left(22+28\right)+\left(23+27\right)+\left(24+26\right)+25\)
\(=50+50+50+50+50+25=275\)
(20+30)+(21+29)+(22+28)+(23+27)+(24+26)+25
=60+50+50+50+50+25
=60+(50×4)+25
=285
20 + 21 + 22+ 23 + 24+ 25 + 26 + 27+ 28 + 29 +30
= (20+30) +.....+( 24+26 ) + 25
= 50+50+50+50 + 25
= 50x4 + 25
= 225
20+21+22+23+24+25+26+27+28+29+30
=(20+30)+(21+29)+(22+28)+23+27)+(24+26)+25
= 50 + 50 + 50 + 50 + 50 +25
= 100 + 100 + 75
= 200 + 75
= 275
20 + 21 + 22+ 23 + 24+ 25 + 26 + 27+ 28 + 29 +30
= ( 20 + 30 ) + ( 21 + 29 ) + ( 22 + 28 ) + ( 23 + 27 ) + ( 24 + 26 ) + 25
= 50 + 50 + 50 + 50 + 50 + 25
= 50 x 5 + 25
= 250 + 25
= 275
=(20 + 30) + (21 + 29 ) + (22 + 28 ) + (23 +27) + (24 + 26 ) + 25
=50 + 50 + 50 + 50 + 50 + 25
= 175
= (20 + 30 ) + (21 + 29 ) + (22 + 28 ) + ( 23 + 27 ) + (24 + 26 ) + 25
= 50 + 50 + 50 + 50 + 50 + 25
= 275
