Toán Lớp 3: Tính nhanh
A=1++3+4+5+6++8+9+10+11+1+13+14+15+16+17+18+19
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Toán Lớp 3: Tính nhanh
A=1++3+4+5+6++8+9+10+11+1+13+14+15+16+17+18+19
Comments ( 2 )
1+2+3+4+5+6++8+9+10+11+1+13+14+15+16+17+18+19.
=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+10.
=(20+20)+(20+20)+(20+20)+(20+20)+(20+10).
=(40+40)+(40+40)+30.
=80+80+30.
=160+30.
=190.
Giải đáp:
A= $\text{190}$
Lời giải và giải thích chi tiết:
A= 1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19
A= (1+19)+ (2+18)+ (3+17)+ (4+16)+ (5+15)+ (6+14)+ (7+13)+ (8+12)+ (9+11)+ 10
A= 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 10
A= 20 x 9 + 10
A= 180 + 10
A= \text{190}