Bài 2 trang 71 Toán 6 Tập 2 | Cánh diều Giải Toán lớp 6

Tính một cách hợp lí:

a) $\left(\frac{617}{191}+\frac{29}{33}-\frac{115}{117}\right).\left(\frac{1}{4}-\frac{1}{5}-\frac{1}{20}\right)$

b) $\frac{12}{5}.\left(\frac{10}{3}-\frac{5}{12}\right)$;

c) 1,23 – 5,48 + 8,77 – 4,32;

d) 7 . 0,25 + 9 . 0,25.

Lời giải

a) $\left(\frac{617}{191}+\frac{29}{33}-\frac{115}{117}\right).\left(\frac{1}{4}-\frac{1}{5}-\frac{1}{20}\right)$

$=\left(\frac{617}{191}+\frac{29}{33}-\frac{115}{117}\right).\left(\frac{5}{20}-\frac{4}{20}-\frac{1}{20}\right)$

$=\left(\frac{617}{191}+\frac{29}{33}-\frac{115}{117}\right).\left(\frac{5-4-1}{20}\right)$

$=\left(\frac{617}{191}+\frac{29}{33}-\frac{115}{117}\right).0$

= 0.

b) $\frac{12}{5}.\left(\frac{10}{3}-\frac{5}{12}\right)$

$=\frac{12}{5}.\left(\frac{40}{12}-\frac{5}{12}\right)$

$=\frac{12}{5}.\left(\frac{40-5}{12}\right)$

$=\frac{12}{5}.\frac{35}{12}$

= 7.

c) 1,23 – 5,48 + 8,77 – 4,32

= (1,23 + 8,77) + (–5,48 – 4,32)

= 10 + ( –10)

= 0.

d) 7.0,25 + 9.0,25

= 0,25. (7 + 9)

= 0,25.16

= 4.