Question

so sánh phân số 

a) \(\dfrac{5}{7}và\dfrac{7}{9};b\dfrac{16}{36}và\dfrac{4}{7}c;\dfrac{13}{15}và\dfrac{11}{12}\)

Answer 1

a, Mẫu số chung : \(63\)

\(\dfrac{5}{7}=\dfrac{5.9}{7.9}=\dfrac{45}{63}\\ \dfrac{7}{9}=\dfrac{7.7}{9.7}=\dfrac{49}{63}\\ 45< 49\\ =>\dfrac{5}{7}< \dfrac{7}{9}\)

b, Mẫu số chung là 63

\(\dfrac{16}{36}=\dfrac{4}{9}=\dfrac{4.7}{9.7}=\dfrac{28}{63}\)

\(\dfrac{4}{7}=\dfrac{4.9}{7.9}=\dfrac{36}{63}\)

\(36>28\\ =>\dfrac{16}{36}>\dfrac{4}{7}\)

c, Mẫu số chung : \(60\)

\(\dfrac{13}{15}=\dfrac{13.4}{15.4}=\dfrac{52}{60}\\ \dfrac{11}{12}=\dfrac{11.5}{12.5}=\dfrac{55}{60}\\ 52< 55\\ =>\dfrac{13}{15}< \dfrac{11}{12}\)

Answer 2

a) 5/7=45/63

7/9=49/63

\(\dfrac{5}{7}< \dfrac{7}{9}\)

b) \(\dfrac{16}{36}=\dfrac{112}{252}\)

\(\dfrac{4}{7}=\dfrac{144}{252}\)

=> \(\dfrac{16}{36}< \dfrac{4}{7}\)