thực hiện phép tính bằng cách thuận tiện
a, 50% + 7/12 -1/2 b,2014 . 65+2014.45-2014.10
c,125-25:3.12 d,(2013.2014+2014.2015+2015+2016)+(1+1/3-1và 1/3)
e,17,75+16,25+14,75+13,25+...........+4,25+2,75+1,25
đúng hết thì mình tick cho nha!
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\(a,50\%+\dfrac{7}{12}-\dfrac{1}{2}\\ =\dfrac{1}{2}+\dfrac{7}{12}-\dfrac{1}{2}\\ =\left(\dfrac{1}{2}-\dfrac{1}{2}\right)+\dfrac{7}{12}\\ =\dfrac{7}{12}\\ b,2022\times67+2022\times43-2022\times10\\ =2022\times\left(67+43-10\right)\\ =2022\times100\\ =202200.\\ c,125-25:3\times12\)
\(=25\times5-25:3\times12\\ =25\times\left(5-\dfrac{1}{3}\right)\times12\\ =25\times\dfrac{14}{3}\times12\\ =1400\)
a,50%+127−21=21+127−21=(21−21)+127=127b,2022×67+2022×43−2022×10=2022×(67+43−10)=2022×100=202200.c,125−25:3×12
\(A=1+\dfrac{1}{5}+\dfrac{1}{25}+\dfrac{1}{125}+...+\dfrac{1}{625}+\dfrac{1}{78125}\)
\(=1+\dfrac{1}{5}+\dfrac{1}{5^2}+\dfrac{1}{5^3}+...+\dfrac{1}{5^7}\)
\(5A=5+1+\dfrac{1}{5}+\dfrac{1}{5^2}+...+\dfrac{1}{5^6}\)
\(\Leftrightarrow5A-A=5+1+\dfrac{1}{5}+\dfrac{1}{5^2}+...+\dfrac{1}{5^6}-1-\dfrac{1}{5}-\dfrac{1}{5^2}-\dfrac{1}{5^3}-...-\dfrac{1}{5^7}\)
\(\Leftrightarrow4A=5-\dfrac{1}{5^7}\Leftrightarrow A=\dfrac{5-\dfrac{1}{5^7}}{4}=\dfrac{\dfrac{390624}{78125}}{4}=\dfrac{390624}{312500}=\dfrac{97656}{78125}\)
\(50\%+\dfrac{7}{12}-\dfrac{1}{2}\)
\(=\dfrac{1}{2}+\dfrac{7}{12}-\dfrac{1}{2}\)
\(=\left(\dfrac{1}{2}-\dfrac{1}{2}\right)+\dfrac{7}{12}\)
\(=\dfrac{7}{12}\)
_______________
\(2022\cdot67+2022\cdot43-2022\cdot10\)
\(=2022\cdot\left(67+43-10\right)\)
\(=2022\cdot100\)
\(=202200\)
_____________________
\(10,3+6,9+8,7+13,1\)
\(=\left(13,1+6,9\right)+\left(10,3+8,7\right)\)
\(=20+19\)
\(=39\)
___________________
\(17,58\times43+57\times17,58\)
\(=17,58\times\left(43+57\right)\)
\(=17,58\times100\)
\(=1758\)
tớ ghi sai nên cập nhật lại câu hỏi, phần 3 các bạn trả lời sớm mà bị sai thì bỏ qua cho tớ nhé
a) 5 . 125 . 2 . 41 . 8
= (5 . 8) . (125 . 2) . 41
= 40 . 250 . 41
= 10 000 . 41
= 410 000
b) 25 . 7 . 10 . 4
= (25 . 4 ) . (10 . 7)
= 100 . 70
= 7000
Chúc bạn học tốt!! ^^
a,5.125.2.41.8=(125.8).(2.5).41=1000.10.41=410000
b,25.7.10.4=(25.4).70=100.70=7000
c,8.12.125.2=(8.125).12.2=100.24=2400
d,4.36.25.50=(4.25).(2.50).18=100.100.18=180000
50% + 7/12 - 1/2
= 1/2 + 7/12 - 1/2
= (1/2 - 1/2) + 7/12
= 0 + 7/12 = 7/12
b) 2014 . 65 + 2014 . 45 - 2014 .10
= 2014 . (65 + 45 - 10)
= 2014 . 100 = 201400
\(2014.65+2014.45-2014.10\)
\(=2014.\left(65+45-10\right)\)
\(=2014.100=201400\)