Question

[Bùi Thị Mai Hiên]

Tính bằng cách thuận tiện nhất: 1 + 5/15 x 2/7 + 1/5 x 2/7

Answer 1

[Nguyễn Lê Phước Thịnh]

\(1+\dfrac{5}{15}\times\dfrac{2}{7}+\dfrac{1}{5}\times\dfrac{2}{7}\)

\(=1+\dfrac{1}{3}\times\dfrac{2}{7}+\dfrac{1}{5}\times\dfrac{2}{7}\)

\(=1+\dfrac{2}{7}\times\left(\dfrac{1}{3}+\dfrac{1}{5}\right)\)

\(=1+\dfrac{2}{7}\times\dfrac{8}{15}=1+\dfrac{16}{105}=\dfrac{121}{105}\)

Answer 2

[Nguyễn Quang Tâm]

\(1+\dfrac{5}{15}\text{x}\dfrac{2}{7}+\dfrac{1}{5}\text{x}\dfrac{2}{7}=1+\left(\dfrac{5}{15}+\dfrac{1}{5}\right)\text{x}\dfrac{2}{7}=1+\dfrac{8}{15}\text{x}\dfrac{2}{7}=1+\dfrac{16}{105}=\dfrac{121}{105}\)