18+12
tính nhanh (15-15/7-15/12-15/98):(18-18/7-18/12-18/98)
tim x biet:
x - 36 : 18 = 12
(x - 36) : 18 = 12
1) \(x-36:18=12\)
\(\Rightarrow x-2=12\)
\(\Rightarrow x=14\)
2) \(\left(x-36\right):18=12\)
\(\Rightarrow x-36=216\)
\(\Rightarrow x=252\)
32.(18-12)-18.(32-12)
32.(18-12)-18.(32-12)
32.6-18.10
192-180
12
32.(18 - 12) - 18(32 - 12) = 32.18 - 18.32 - 32.12 + 18.12 = (18 - 32).12 = (-14).12 = (-4).6.7 = (-4).42 = 168
\(\frac{15-\frac{15}{7}-\frac{15}{12}-\frac{15}{98}}{18-\frac{18}{7}-\frac{18}{12}-\frac{18}{98}}\)
\(\frac{15-\frac{15}{7}-\frac{15}{12}-\frac{15}{98}}{18-\frac{18}{7}-\frac{18}{12}-\frac{18}{98}}\)= \(\frac{15-15\left(\frac{1}{7}+\frac{1}{12}+\frac{1}{98}\right)}{18-18\left(\frac{1}{7}+\frac{1}{12}+\frac{1}{98}\right)}\)=\(\frac{15\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}{18\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}\)= \(\frac{15}{18}\)=\(\frac{5}{6}\)
tính nhanh
15-15/7-15/12-15/98=?
và:18-18/7-18/12-18/98=?
giúp tôi nhé!
\(\frac{15-\frac{15}{7}-\frac{15}{12}-\frac{15}{98}}{18-\frac{18}{7}-\frac{18}{12}-\frac{18}{98}}\)
\(\frac{15-\frac{15}{7}-\frac{15}{12}-\frac{15}{98}}{18-\frac{18}{7}-\frac{18}{12}-\frac{18}{98}}=\frac{15\left(1+\frac{1}{7}+\frac{1}{12}+\frac{1}{98}\right)}{18\left(1+\frac{1}{7}+\frac{1}{12}+\frac{1}{98}\right)}=\frac{15}{18}=\frac{5}{6}\)
bài 2: rút gọn rồi tính
a) 8/5 -18/27 =.................................................. .................................................. b)12/20-6/18............................................ c)18/21-12/27...................................... d)8/12-20/50................................................. |
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a: =8/5-2/3=24/15-10/15=14/15
12/20-6/18=3/5-1/3=9/15-5/15=4/15
b: 18/21-12/27=6/7-7/9=54/63-49/63=5/63
8/12-20/50=2/3-2/5=10/15-6/15=4/15
\(a,\dfrac{8}{5}-\dfrac{18}{27}=\dfrac{8}{5}-\dfrac{2}{3}=\dfrac{14}{15}\\ \dfrac{12}{20}-\dfrac{6}{18}=\dfrac{3}{5}-\dfrac{1}{3}=\dfrac{4}{15}\\ b,\dfrac{18}{21}-\dfrac{12}{27}=\dfrac{6}{7}-\dfrac{4}{9}=\dfrac{26}{63}\\ \dfrac{8}{12}-\dfrac{20}{50}=\dfrac{2}{3}-\dfrac{2}{5}=\dfrac{4}{15}\)
a) 8/5 -18/27 = 8/5 - 2/3 = 14/15 12/20 - 6/18 = 3/5 - 1/3 = 4/15 b) 18/21 - 12/27 = 6/7 - 4/9 = 26/63 8/12 - 20/50 = 2/3 - 2/5 = 4/15 |
Rút gọn rồi tính: a)5/8+18/27 b)12/20+6/18 c)8/12+20/30 đ)10/12+12/36
b: 12/20+6/18=3/5+1/3=9/15+5/15=14/15
c: 8/12+20/30=2/3+2/3=4/3
d: 10/12+12/36=5/6+2/6=7/6
Tính nhanh
15-15 phần 7-15 phần 12-15 phần 98
18-18 phần 7 - 18 phần 12 - 18 phần 98
\(15-\frac{15}{7}-\frac{15}{12}-\frac{1}{98}\)
\(=15\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)\)
\(=15x\frac{449}{588}=\frac{2245}{196}\)
\(18-\frac{18}{7}-\frac{18}{12}-\frac{18}{98}\)
\(=18\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)\)
\(=18x\frac{449}{588}=\frac{1347}{98}\)
x-x/12+x/18/7-7/12+7/18=-4/7
\(x-\dfrac{x}{12}+\dfrac{x}{\dfrac{18}{7}}-\dfrac{7}{12}+\dfrac{7}{18}=-\dfrac{4}{7}\)
\(\Rightarrow x\left(1-\dfrac{1}{12}+\dfrac{1}{\dfrac{18}{7}}\right)=-\dfrac{4}{7}+\dfrac{7}{12}-\dfrac{7}{18}\)
\(\Rightarrow x\left(\dfrac{216-18+7}{12.18}\right)=\dfrac{-864+882-588}{7.12.18}\)
\(\Rightarrow x\left(\dfrac{205}{12.18}\right)=\dfrac{-570}{7.12.18}\)
\(\Rightarrow x=\dfrac{-570}{7.12.18}.\dfrac{12.18}{205}\)
\(\Rightarrow x=\dfrac{-114}{287}\)