Câu 1:
Cách 1:
`(2/3×4/5)×5/6=8/15×5/6=(8×5)/(15×6)=(2×2×2×5)/(3×5×2×3)=4/9`
Cách 2:
`(2/3×4/5)×5/6=2/3×(4/5 ×5/6)=2/3×4/6=(2×4)/(3×6)=(2×4)/(3×2×3)=4/9`
Câu 2:
Cách 1:
`(1/2+1/3)×1/5=((3+2)/6)×1/5=5/6×1/5=1/6`
Cách 2:
`(1/2+1/3)×1/5=1/2×1/5+1/3×1/5=1/10+1/15=3/30+2/30=5/30=1/6`