Question

[Nguyễn Diệu Anh]

Bài 2. Tính bằng cách hợp lý:

 a) 3 /5 + 6/ 11 + 7/ 13 + 2 /5 + 16 /11 + 19/ 13

b) 5 /8 + 5/ 12 - 1 /8 + 1/ 1/2

𝑐) 3 /2 × 4 /7 + 3/ 7 × 3/ 2

d) 17 /14 × 3/ 7 + 4 /7 × 17 /14 − 17/ 14

Bài 3. Tính giá trị biểu thức:

a) 2/ 3 × 10/ 21 × 3 /2

b) 22/ 5 × 1/2 × 5 /22

c ) 7/ 2 × 23/ 81 × 2 /7

d) 5 /17 × 21/ 4 × 35 /15 × 1/ 7

Answer 1

[Akai Haruma]

Bài 2:

a. $=(\frac{3}{5}+\frac{2}{5})+(\frac{6}{11}+\frac{16}{11})+(\frac{7}{13}+\frac{19}{13})=\frac{5}{5}+\frac{22}{11}+\frac{26}{13}$

$=1+2+2=5$

b. $=(\frac{5}{8}-\frac{1}{8})+(\frac{5}{12}+\frac{1}{12})$

$=\frac{4}{8}+\frac{6}{12}=\frac{1}{2}+\frac{1}{2}=1$

c.

$=\frac{3}{2}\times (\frac{4}{7}+\frac{3}{7})=\frac{3}{2}\times 1=\frac{3}{2}$

d.

$=\frac{17}{14}\times (\frac{3}{7}+\frac{4}{7}-1)$

$=\frac{17}{14}\times 0=0$

Answer 2

[Akai Haruma]

Bài 3:

a.$=(\frac{2}{3}\times \frac{3}{2})\times \frac{10}{21}=1\times \frac{10}{21}=\frac{10}{21}$
b. $=(\frac{22}{5}\times \frac{5}{22})\times \frac{1}{2}=1\times \frac{1}{2}=\frac{1}{2}$
c. $=(\frac{7}{2}\times \frac{2}{7})\times \frac{23}{81}=1\times \frac{23}{81}=\frac{23}{81}$

d. $=\frac{5\times 21\times 35\times 1}{17\times 4\times 15\times 7}$

$=\frac{5\times 3\times 7\times 5\times 7}{17\times 4\times 3\times 5\times 7}$

$=\frac{5\times 7}{17\times 4}=\frac{35}{68}$