98+28+17+12+19+21=98+(28+12)+17+(19+21)
=98+40+17+40
=195
98+28+17+12+19+21=98+(28+12)+17+(19+21)
=98+40+17+40
=195
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29=bn
ai nhanh mk tick cho,nhớ kb với mk nha
28+27+26+25+24+23+22+21+20+19+18+17+16+15+14+13+12+11+10+9+8+7+6+5+4+3+2+1+=....................................................?
Hãy tính phép tính tính nhanh sau:
10+11+12+13+14+15+16+17+18+19+20
2, Tính bằng cách hợp lí
a, 14-11+16-13+19-15+21-17
b, 4-6+8-10+12-14+16-18+20
hãy tính nhanh:
A.1+2+3+4+5+6+7+8+9+10+11+12+13-14=?
B.30-29+28-27+26-25+24-23+22-21...+12-11+10-9+8-7+6-5+4-3+2-1=?
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50+51+52+53+54+56+57+58+59+60+61+62+63+64+65+66+67+68+69+70=?
Điền dấu > , < , =
19 + 7....19 + 9 17 + 7....17 + 9
17 + 9....19 + 7 37 + 15....55−1
38−8....23 + 7 28−3....17 + 6
17+28:3+47-12+98+1004x7:8
tk cho bạn nào nhanh nhất
Tính nhanh
10+11+12+13+14+16+17+18+19+20
1+2+3+4+5+6+7+8+9
Help help me giúp cần gấp