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( 18 x 987 + 9 x 345 x2 - 3 x 621 x 6 ) : 72
= ( 17766 + 3186 x 2 - 1863 x 6 ) : 72
= ( 17766 + 6372 - 11178 ) : 72
= ( 24138 - 11178 ) : 72
= 12960 : 72
= 180
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\(72\cdot3+72\cdot6+72=72\cdot\left(3+6+1\right)=72\cdot10=720\)
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58 + 92 -73:11
=58 + 92 -73/11
=150-73/11
=1577/11
25+72:(24+1)+72
=25+72:25+72
=25+2,88+72
=27,88+72
=99,88
\(=150-\frac{73}{11}=\frac{1577}{11}\)
\(=25+72:25+72=25+72:\left(25+1\right)=25+72:26=25+3=28\)
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`1/42 + 1/56 + 1/72 + .... + 1/9900`
`= 1/( 6*7) + 1/( 7*8 ) + ..... + 1/( 99*100)`
`= 1/6 - 1/7 + 1/7-1/8+....+1/99-1/100`
`= 1/6 - 1/100`
`= 50/300 - 3/300`
`= 47/300`
\(\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+...+\dfrac{1}{9900}\\ =\dfrac{1}{6.7}+\dfrac{1}{7.8}+\dfrac{1}{8.9}+...+\dfrac{1}{99.100}\\ =\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{9}+...+\dfrac{1}{99}-\dfrac{1}{100}\\ =\dfrac{1}{6}-\dfrac{1}{100}=\dfrac{47}{300}\)
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`(64×15×9)/(72×45×6) `
`=(8xx8×3xx5×9)/(8xx9×5xx9×2xx3) `
`=8/(9×2) `
`= 4/9`
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a.(64 - 32 ) :8 = 32 : 8 = 4
b. 36 x 2 x7 + 36 x 86
= 36 x (14 + 86)
= 36 x 100
= 3600
68:8 - 32 : 8
= ( 68 - 32): 8
= 36 : 8
= 4,5
72 x 7 + 36 x 86
= 72 x 7 + 36 x 2 x 43
= 72 x 7 + 72 x 43
= 72 x ( 7 + 43)
= 72 x 50
= 3600