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21/17 x 13/14 x 56 x 3/42
= 39/34 x 56 x 3/42
= 1092/17 x 3/42
= 78/17
\(\dfrac{21}{17}\times\dfrac{13}{14}\times56\times\dfrac{3}{42}\)
\(=\dfrac{21}{17}\times\dfrac{13}{14}\times56\times\dfrac{1}{14}\)
\(=\dfrac{21\times13\times56}{17\times14\times14}\)
\(=\dfrac{3\times7\times13\times14\times2\times2}{17\times2\times7\times14}\)
\(=\dfrac{3\times13\times2}{17}\)
\(=\dfrac{78}{17}\)
| #Sahara |
a) C1 : \(\left(\frac{1}{2}+\frac{1}{3}\right)\times\frac{2}{5}=\left(\frac{3}{6}+\frac{2}{6}\right)\times\frac{2}{5}\)
\(=\frac{5}{6}\times\frac{2}{5}\)
\(=\frac{10}{30}=\frac{1}{3}\)
C2 : \(\left(\frac{1}{2}+\frac{1}{3}\right)\times\frac{2}{5}=\frac{1}{2}\times\frac{2}{5}+\frac{1}{3}\times\frac{2}{5}\)
\(=\frac{1}{5}+\frac{2}{15}\)
\(=\frac{3}{15}+\frac{2}{15}\)
\(=\frac{5}{15}=\frac{1}{3}\)
b) C1 : \(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}=\frac{17}{35}+\frac{34}{105}\)
\(=\frac{51}{105}+\frac{34}{105}\)
\(=\frac{85}{105}=\frac{17}{21}\)
C2 : \(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}=\frac{17}{21}\times\left(\frac{3}{5}+\frac{2}{5}\right)\)
\(=\frac{17}{21}\times1=\frac{17}{21}\)
b,21/17x13/14x56x3/42
=21/17x3/42x56x13/14
=21x3/17x42 x 56x13/14
=21x3/17x21x2 x 14x4x13/14
=3/17x2 x 4x13
=3/24 x 52=3x52/24
=3x52/3x8
=52/8=13/2
a, 6/7 x 16/15 x 7/6 x 21/32
=(6/7 x 7/6)x16/15x21/32
=16/15x21/32
=16x21/15x32
=16x3x7/3x5x16x2
=7/5x2=7/10
\(\dfrac{21}{17}\times\dfrac{13}{14}\times56\times\dfrac{3}{42}=\dfrac{78}{17}\)