( 3/8 + 2/8) +1/8= 3/8 + 2/8 +1/8= 3/8 + 3/8= 3/4
3/8 + (2/8 +1/8)= 3/8 + 2/8 +1/8= 3/8 + 3/8= 3/4
( 3/8 + 2/8) + 1/8....3/8+(2/8+1/8)= 3/4+.....+3/4
\(\left(\frac{3}{8}+\frac{2}{8}\right)+\frac{1}{8}=\frac{3}{8}+\left(\frac{2}{8}+\frac{1}{8}\right)=\frac{3}{8}+\frac{3}{8}=\frac{6}{8}=\frac{3}{4}\) (tính chất kết hợp)
\(\Rightarrow\left(\frac{3}{8}+\frac{2}{8}\right)+\frac{1}{8}=\frac{3}{8}+\left(\frac{1}{8}+\frac{2}{8}\right)\)
( 3/8 + 2/8 ) + 1/8
= 5/8 + 1/8
= 6/8
3/8 ( 2/8 + 1/8 )
= 3/8 + 3/8
= 6/8
( 3/8 + 2/8 ) + 1/8 = 3/8 + ( 2/8 + 1/8 )