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Lời giải:
14 giờ 25 phút x 8 =112 giờ 200 phút = 115 giờ 20 phút.
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\(\dfrac{1}{2}\) \(\times\) \(\dfrac{6}{7}\) + \(\dfrac{5}{7\times5}\) - \(\dfrac{8}{9}\)
= \(\dfrac{3}{7}\) + \(\dfrac{1}{7}\) - \(\dfrac{8}{9}\)
= \(\dfrac{4}{7}\) - \(\dfrac{8}{9}\)
= - \(\dfrac{20}{63}\)
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30/x - 2 = 36/42
30/x - 2 = 6/7
30/x = 6/7 + 2
30/x = 20/7
60/Xx2 = 60/21 (bước quy đồng)
Xx2 = 21
X = 21 : 2
X = 21/2
_HT_
\(\frac{30}{x}\)- 2 = \(\frac{36}{42}\)
\(\frac{30}{x}\)- 2 = \(\frac{6}{7}\)
\(\frac{30}{x}\) = \(\frac{6}{7}\)+ 2
\(\frac{30}{x}\) = \(\frac{20}{7}\)
x = 30 : \(\frac{20}{7}\)
x = \(\frac{21}{2}\)
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\(8h+15'30''+45'+16'\)
\(=8h+15'+30''+45'+16'\)
\(=8h+\left(15'+45'+16'\right)+30''\)
\(=8h+\left(60'+16'\right)+30''\)
\(=8h+\left(1h+16'\right)+30''\)
\(=\left(8h+1h\right)+16'+30''\)
\(=9h+16'+30''\)
\(=9h16'30''\)
8 giờ + 15 phút 30 giây + 45 phút +16 phút
= 9 giờ 30 giây
study well
$YOUTUBER$
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