Question

7,8 x 2 + 3,9 x 8 + 15,6 x 2 - 38

 

Answer 1

\(7,8\times2+3.9\times8+15,6\times2-38\)

\(=3,9\times4+3,9\times8+3,9\times8-38\)

\(=3,9\times\left(4+8+8\right)-38\)

\(=3,9\times20-38\)

\(=78-38=40\)

Answer 2

7,8×2+3.9×8+15,6×2−38

=3,9×4+3,9×8+3,9×8−38

=3,9×(4+8+8)−38

=3,9×20−38

=78−38=40

Answer 3

7 , 8 x 2 + 3 , 9 x 8 + 15 , 6 x 2 - 38 

= 7 , 8 x 2 + 3 , 9 x ( 2 x 4 ) + ( 7 , 8 x 2 ) x 2 - 38 

= 7 , 8 x 2 + ( 3 , 9 x 2 ) x 4 + 7 , 8 x ( 2 x 2 ) - 38 

= 7 , 8 x 2 + 7 , 8 x 4 + 7 , 8 x 4 - 38 

= 7 , 8 x ( 2 + 4 + 4 ) - 38 

= 7 , 8 x 10 - 38 

= 78 - 38 

= 48 

Chúc bạn học tốt !!!