1.tính nhanh a,1/30+1/42+1/56+1/72+1/90 2,tính a,(2-2/5):14/15 b,11/4+5/3:5/2 24/08/2021 Bởi Everleigh 1.tính nhanh a,1/30+1/42+1/56+1/72+1/90 2,tính a,(2-2/5):14/15 b,11/4+5/3:5/2
1. Tính nhanh a) $\frac{1}{30}$+$\frac{1}{42}$+$\frac{1}{56}$+$\frac{1}{72}$+$\frac{1}{90}$ = $\frac{1}{5.6}$+$\frac{1}{6.7}$+$\frac{1}{7.8}$+$\frac{1}{8.9}$+$\frac{1}{9.10}$ = $\frac{1}{5}$-$\frac{1}{6}$+$\frac{1}{6}$-$\frac{1}{7}$+$\frac{1}{7}$-$\frac{1}{8}$+$\frac{1}{8}$-$\frac{1}{9}$+$\frac{1}{9}$-$\frac{1}{10}$ = $\frac{1}{5}$-$\frac{1}{10}$ = $\frac{1}{10}$ 2, Tính a) (2-$\frac{2}{5}$):$\frac{14}{15}$ = $\frac{8}{5}$:$\frac{14}{15}$ = $\frac{12}{7}$ b) $\frac{11}{4}$+$\frac{5}{3}$:$\frac{5}{2}$ = $\frac{11}{4}$+$\frac{2}{3}$ = $\frac{41}{12}$ Bình luận
Bài $1$. $a$) `1/{30} + 1/{42} + 1/{56} + 1/{72} + 1/{90}` `= 1/{5.6} + 1/{6.7} + 1/{7.8} + 1/{8.9} + 1/{9.10}` `= 1/5 – 1/6 + 1/6 – 1/7 + 1/7 – 1/8 + 1/8 – 1/9 + 1/9 – 1/{10}` `= 1/5 – 1/{10}` `= 1/{10}` Bài $2$ $a$) `(2 – 2/5) : {14}/{15}` `= 8/5 : {14}/{15}` `= {12}/7` $b$) `{11}/4 + 5/3 : 5/2` `= 11/4 + 2/3` `= {41}/{12}` Bình luận
1. Tính nhanh
a) $\frac{1}{30}$+$\frac{1}{42}$+$\frac{1}{56}$+$\frac{1}{72}$+$\frac{1}{90}$
= $\frac{1}{5.6}$+$\frac{1}{6.7}$+$\frac{1}{7.8}$+$\frac{1}{8.9}$+$\frac{1}{9.10}$
= $\frac{1}{5}$-$\frac{1}{6}$+$\frac{1}{6}$-$\frac{1}{7}$+$\frac{1}{7}$-$\frac{1}{8}$+$\frac{1}{8}$-$\frac{1}{9}$+$\frac{1}{9}$-$\frac{1}{10}$
= $\frac{1}{5}$-$\frac{1}{10}$
= $\frac{1}{10}$
2, Tính
a) (2-$\frac{2}{5}$):$\frac{14}{15}$
= $\frac{8}{5}$:$\frac{14}{15}$
= $\frac{12}{7}$
b) $\frac{11}{4}$+$\frac{5}{3}$:$\frac{5}{2}$
= $\frac{11}{4}$+$\frac{2}{3}$
= $\frac{41}{12}$
Bài $1$.
$a$) `1/{30} + 1/{42} + 1/{56} + 1/{72} + 1/{90}`
`= 1/{5.6} + 1/{6.7} + 1/{7.8} + 1/{8.9} + 1/{9.10}`
`= 1/5 – 1/6 + 1/6 – 1/7 + 1/7 – 1/8 + 1/8 – 1/9 + 1/9 – 1/{10}`
`= 1/5 – 1/{10}`
`= 1/{10}`
Bài $2$
$a$) `(2 – 2/5) : {14}/{15}`
`= 8/5 : {14}/{15}`
`= {12}/7`
$b$) `{11}/4 + 5/3 : 5/2`
`= 11/4 + 2/3`
`= {41}/{12}`