Toán Lớp 5: 1/2 + 1/6 + 1/9 + 1/81
làm 2 cách ạ .
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Toán Lớp 5: 1/2 + 1/6 + 1/9 + 1/81
làm 2 cách ạ .
Comments ( 2 )
1/2 + 1/6 + 1/12 + 1/20
= 2/3 + 1/12 + 1/20
= 3/4 + 1/20
= 4/5
1/2 + 1/6 + 1/9 + 1/81
= $\dfrac{1}{1×2}$ + $\dfrac{1}{2×3}$ + $\dfrac{1}{3×4}$ + $\dfrac{1}{4×5}$
= 1/1 – 1/2 + 1/2 – 1/3 + 1/3 – 1/4 + 1/4 – 1/5
= 1 – 1/5
= 4/5
text{Giải đáp + Lời giải và giải thích chi tiết :}
C_1 :
1/2 + 1/6 + 1/12 + 1/20
= 1/(1xx2) + 1/(2xx3) + 1/(3xx4) + 1/(4xx5)
= 1/1 – 1/2 + 1/2 – 1/3 + 1/3 – 1/4 + 1/4 – 1/5
= 1/1 – 1/5
= 4/5 .
C_ 2 :
1/2 + 1/6 + 1/12 + 1/20 text{[ MSC : 60 ]}
= (1xx30)/(2xx30) + (1xx10)/(6xx10) + (1xx5)/(12xx5) + (1xx3)/(20xx3)
= 30/60 + 10/60 + 5/60 + 3/60
= (30+10+5+3)/60
= 48/60
= 4/5 .
text{#muoiakiramobile}