Question

B1: Tính

\(\left(8+2\dfrac{1}{3}-\dfrac{3}{5}\right)-\left(5+0,4\right)-\left(3\dfrac{1}{3}-2\right)\)

B3: Tính hợp lí:

\(0,65.78+2\dfrac{1}{5}.2020+0,35.78-2,2.2020\)

Answer 1

Bài 3: 

\(=78\left(0.65+0.35\right)+2020\left(2+\dfrac{1}{5}-2.2\right)\)

=78

Answer 2

b1

\(=\left(8+\dfrac{7}{3}-\dfrac{3}{5}\right)-\left(5+\dfrac{2}{5}\right)-\left(\dfrac{10}{3}-2\right)\\ =8+\dfrac{7}{3}-\dfrac{3}{5}-5-\dfrac{2}{5}-\dfrac{10}{3}+2\\ =\left(8-5+2\right)+\left(\dfrac{7}{3}-\dfrac{10}{3}\right)+\left(-\dfrac{3}{5}-\dfrac{2}{5}\right)\\ =5-1-1=3\)

B3

\(=78\cdot\left(0,65+0,35\right)+2020\cdot\left(2\dfrac{1}{5}-2,2\right)\\ =78\cdot1+2020\cdot\left(\dfrac{11}{5}-\dfrac{11}{5}\right)\\ =78+2020.0=78\)