Question

So sánh các cặp phân số sau bằng cách nhanh nhất:

a) \(\frac{20}{19}\) và \(\frac{79}{80}\)

b) \(\frac{17}{5}\) và \(\frac{9}{4}\)

c) \(\frac{46}{9}\) và \(\frac{36}{7}\)

d) \(\frac{17}{18}\) và \(\frac{2014}{2015}\)

 

Answer 1

a)\(\frac{20}{19}>\)\(\frac{79}{80}\)

vì:\(\frac{20}{19}\)>1

\(\frac{79}{80}\)<1

b)\(\frac{17}{5}\)>\(\frac{9}{4}\)

vì:\(\frac{17}{5}\)=\(\frac{17x4}{5x4}\)=\(\frac{68}{20}\)

\(\frac{9}{4}\)=\(\frac{9x5}{4x5}\)=\(\frac{45}{20}\)

c)\(\frac{46}{9}\)>\(\frac{36}{7}\)

vì:\(\frac{46}{9}\) \(\frac{9x4}{7}\)

46/9 =46          9x4/7=4/7

d)\(\frac{17}{18}\)>\(\frac{2014}{2015}\)

vì:\(\frac{18}{18}\)-\(\frac{17}{18}\)=\(\frac{1}{18}\)

\(\frac{2015}{2015}-\frac{2014}{2015}\)=\(\frac{1}{2015}\)

 

 

 

Answer 2

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