Tính hơp lý (nếu có thể)
a)(-2/5.4/15+(-3/10).4/15
B)21-3 3/4:(3/8-1/6)
c)(-5/6+2/5):3/8+(4/5-11/30):3/8
em cần gấp ạ
Tính hơp lý (nếu có thể) a)(-2/5.4/15+(-3/10).4/15 B)21-3 3/4:(3/8-1/6) c)(-5/6+2/5):3/8+(4/5-11/30):3/8 em cần gấp ạ
By Charlie
a)(-2/5).4/15+(-3/10).4/15= 4/15. [ (-2/5) + (-3/10) ]
= 4/15. (-4/10) + (-3/10)
= 4/15 . (-7/10)
= -14/75
b,21-3 3/4:(3/8-1/6) = 21 – 15/4 : ( 9/24 – 4/24 )
= 21 – (15/4 : 5/24)
= 21 – ( 15/4 . 24/5)
= 21 – 360/20
= 21 – 18
= 3
c)(-5/6+2/5):3/8+(4/5-11/30):3/8 = (-5/6+2/5).8/3 + (4/5-11/30).8/3
= 8/3. [(-5/6)+2/5 + 4/5-11/30 ]
= 8/3. [(-25/30) – 11/30] + (2/5 + 4/5)
= 8/3. [(-36/30) + 6/5]
= 8/3. [( -6/5 )+ 6/5 ]
= 8/3. 0
= 0
Đáp án:
a) `(-2/5. 4/15+(-3/10). 4/15`
`= 4/15.[-2/5+(-3/10)]`
`=4/15.-7/10= -14/75`
b)`21-3 3/4:(3/8-1/6)`
`=21 – 15/4: 5/24`
`=21-18`
`=3`
c)`(-5/6+2/5):3/8+(4/5-11/30):3/8`
`=-13/30. 8/3 + 13/30. 8/3`
`=8/3. (-13/30+13/30)`
`=8/3. 0= 0`