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\(\left(2+4+6+8+...+100\right)\times\left(15\times3-15\times2-15\right)\)
\(=\left[102\times50\div2\right]\times\left[15.\left(3-2-1\right)\right]\)
\(=2550\times0\)
\(=0\)
\(a,\frac{42}{25}:\frac{y}{5}=\frac{6}{5}\)
\(\frac{y}{5}=\frac{42}{25}:\frac{6}{5}\)
\(\frac{y}{5}=\frac{42}{25}\times\frac{5}{6}\)
\(\frac{y}{5}=\frac{7}{5}\)
\(\Leftrightarrow5y=7.5\)
\(5y=35\)
\(y=7\)
y x 3/7 = 13/15 - 2/5
y x 3/7 = 7/15
y = 7/15 : 3/7
y = 49/45
Vậy y = 49/45
\(Y\cdot\frac{3}{7}=\frac{13}{15}-\frac{2}{5}\)
=>\(Y\cdot\frac{3}{7}=\frac{7}{15}\)
=>\(Y=\frac{7}{15}:\frac{3}{7}=\frac{49}{45}\)
( dấu . là * đó)
a) y + 3/7 x 21/9 = 5
y + 3/7 x 7/3 = 5
y + 1 = 5
y = 4
b) y x 3/5 - 1/2 = 4/5
y x 3/5 = 4/5 + 1/2
y x 3/5 = 13/10
y = 13/6
c) 9/8 - y + 2/5 = 1/4
y - 2/5 = 9 /8 - 1/4
y - 2/5 = 7/8
y = 51/40
d) y - 6/5 : 2/3 = 5/6
y - 9/5 = 5/6
y = 79/30
e) y : 7/8 + 3/4 = 7/4
y : 7/8 = 1
y = 7/8
\(\frac{4}{15}:y=\left(\frac{4}{5}+\frac{1}{2}\right)\times\frac{4}{13}\)
\(\frac{4}{15}:y=\frac{13}{10}\times\frac{4}{13}\)
\(\frac{4}{15}:y=\frac{2}{5}\)
\(y=\frac{4}{15}:\frac{2}{5}\)
\(y=\frac{2}{3}\)
\(\frac{4}{15}:y=\left(\frac{4}{5}+\frac{1}{2}\right)\times\frac{4}{13}\)
\(\frac{4}{15}:y=\frac{13}{10}\times\frac{4}{13}\)
\(\frac{4}{15}:y=\frac{2}{5}\)
\(y=\frac{4}{15}:\frac{2}{5}\)
\(y=\frac{2}{3}\)
\(\frac{4}{15}:y=\left(\frac{8}{10}+\frac{5}{10}\right)X\frac{4}{13}\)
\(\frac{4}{15}:y=\frac{13}{10}X\frac{4}{13}\)
\(\frac{4}{15}:y=\frac{2}{5}\)
\(y=\frac{4}{15}:\frac{2}{5}\)
\(y=\frac{4}{15}X\frac{5}{2}\)
\(y=\frac{2}{3}\)
HOK TỐT
\(\text{x+5+y+5+x+5+y+5}=2\left(x+y\right)+20\)
\(=2.20+20\)
\(=60\)
x+5+y+5+x+5+y+5 = x+y+x+y+5x4 = 20 + 20 + 20 = 20 x 3 = 60
\(\dfrac{2}{15}:y=\dfrac{8}{5}-\dfrac{2}{5}\)
\(\dfrac{2}{15}:y=\dfrac{6}{5}\)
\(y=\dfrac{2}{15}:\dfrac{6}{5}\)
\(y=\dfrac{90}{10}=9\)
Nhớ quy tắc:
x : y = ...
=> y = x: ...
=> x = ... nhân y
Tương tự áp dụng với cách làm suy ra:
y = 2/ 15 : (8/5 - 2/5)