Đáp án + Giải thích các bước giải:
Bài 1: Thực hiện phép tính:
a, `(136/15 - 28/5 + 62/10) . 21/24`
` = ( 272/30 - 168/30 + 192/30) . 7/8`
` = 29/3 . 7/8`
` = 203/24`
b, `1,4 . 45/49 - (4/5 + 2/3) : 2 1/5`
` = 7/5 . 45/49 - (12/15 + 10/15) : 11/5`
` = 9/7 - 22/15 : 11/5`
` = 9/7 - 2/3`
` = 27/21 - 14/21`
` = 13/21`
c, `1 3/8 + 1/8 : (0,75 - 1/2) - 25% . 1/2`
`= 11/8 + 1/8 : (3/4 - 1/2) - 1/4 . 1/2`
`= 11/8 + 1/8 : 1/4 - 1/8`
`= 11/8 + 4/8 - 1/8`
`= 14/8 = 7/4`
d, `(142/24 + 41/4 - 54/12 + 63/54). (-1/2)^2`
` = ( 71/12 + 124/12 - 54/12 + 14/12) . 1/4`
` = 77/6 . 1/4`
` = 77/24`
Bài 2: Tính hợp lý
a, `(6 4/9 + 3 7/11) - 4 4/9`
` = 6 4/9 + 3 7/11 - 4 4/9`
` = (6 4/9 - 4 4/9) + 3 7/11`
` = 2 + 3 7/11`
` = 5 7/11 = 62/11`
b, `11 3/13 - (2 4/7 + 5 3/13)`
` = 11 3/13 - 2 4/7 - 5 3/13`
` = (11 3/13 - 5 3/13) - 2 4/7`
` = 6 - 2 4/7`
` = 3 3/7 = 24/7`
c, `6/25 . 7/3 + 19/25 . 7/3`
` = 7/3 . (6/25 + 19/25)`
` = 7/3 . 1 = 7/3`
d, `(1/4 + -5/13) + (2/11 + -8/13 + 3/4)`
` = 1/4 - 5/13 + 2/11 - 8/13 + 3/4`
` = (1/4 + 3/4) - (5/13 + 8/13) + 2/11`
` = 1 - 1 + 2/11`
` = 2/11`
e, `5/7 . 5/11 + 5/7 . 2/11 - 5/7 . 14/11`
` = 5/7 . (5/11 + 2/11 - 14/11)`
` = 5/7 . -7/11`
` = -5/11`
f, `6/7 + 1/7 . 2/7 + 1/7 . 5/7`
` = 6/7 + 1/7 . (2/7 + 5/7)`
` = 6/7 + 1/7 . 1`
` = 6/7 + 1/7`
` = 7/7 = 1`