Question

Cho :

             \(A=\left[0,8.7+\left(0,8\right)^2\right]\left(1,25.7-\dfrac{4}{5}.1,25\right)+31,64\)

             \(B=\dfrac{\left(1,09-0,29\right).\dfrac{5}{4}}{\left(18,9-16,65\right).\dfrac{8}{9}}\)

Hỏi A gấp mấy lần B ?

 

Answer 1

Ta có :

A = \(\left[0,8.7+\left(0,8\right)^2\right].\left(1,25.7-\dfrac{4}{5}.1,25\right)+31,64\)

A = \(\left[0,8.\left(7+0,8\right)\right].\left[1,25.\left(7-\dfrac{4}{5}\right)\right]+31,64\)

A = \(\left(0,8.7,8\right)\left(1,25.6,2\right)+31,64\)

A = 6,24 . 7,75 + 31,64

A = 48,36 + 31,64

A = 80

B = \(\dfrac{\left(1,09-1,29\right).\dfrac{5}{4}}{\left(18,9-16,25\right).\dfrac{8}{9}}\)

B= \(\dfrac{\dfrac{4}{5}.\dfrac{5}{4}}{\dfrac{9}{4}.\dfrac{8}{9}}\)

B = \(\dfrac{1}{2}\)

Vậy A gấp B : 80 :\(\dfrac{1}{2}\) = 160 (lần)

Answer 2

Ta có : A = [0,8.7 + (0,8)²](1,25.7 - (4/5).1,25)+31,64

= 0,8.(7 + 0,8).1,25 (7 - 0,8)+ 31,64

= 0,8.7,8.1,25.6,2 + 31,64

= 1.48,36 + 31,64 = 80

Ta có: A : B = 80 : (1/2) = 80.(2/1)=160

Vậy A gấp B là 160 lần