Question

Quy đồng mẫu các phân số

f) \(\dfrac{165}{270}\) ; \(\dfrac{91}{156}\) ; \(\dfrac{210}{1134}\)

g) \(\dfrac{21}{9}\) ; \(\dfrac{120}{50}\) ; \(\dfrac{63}{54}\)

h) \(\dfrac{75}{500}\) ; \(\dfrac{150}{90}\) ; \(\dfrac{250}{900}\)

bài 18: tìm 2 số tự nhiên a, b biết rằng a + b = 128 và ƯCLN (a,b) = 16

 

nhanh + chi tiết = tick

Answer 1

f, \(\dfrac{165}{270}\) = \(\dfrac{165:15}{270:15}\) = \(\dfrac{11}{18}\) = \(\dfrac{11\times6}{18\times6}\) = \(\dfrac{66}{108}\)

 \(\dfrac{91}{156}\) = \(\dfrac{91:13}{156:13}\) = \(\dfrac{7}{12}\) = \(\dfrac{7\times9}{12\times9}\) = \(\dfrac{63}{108}\)

\(\dfrac{210}{1134}\) = \(\dfrac{210:42}{1134:42}\) = \(\dfrac{5}{27}\) =  \(\dfrac{5\times4}{27\times4}\) = \(\dfrac{20}{108}\)

 

Answer 2

g, \(\dfrac{21}{9}\) = \(\dfrac{21:3}{9:3}\) = \(\dfrac{7}{3}\) = \(\dfrac{7\times10}{3\times10}\) = \(\dfrac{70}{30}\)

     \(\dfrac{120}{50}\) =  \(\dfrac{120:10}{50:10}\) = \(\dfrac{12}{5}\) = \(\dfrac{12\times6}{5\times6}\) = \(\dfrac{72}{30}\)

       \(\dfrac{63}{54}\) = \(\dfrac{63:9}{54:9}\) = \(\dfrac{7}{6}\)  = \(\dfrac{7\times5}{6\times5}\) = \(\dfrac{35}{30}\)

      

Answer 3

h, \(\dfrac{75}{100}\) = \(\dfrac{75:25}{100:4}\) = \(\dfrac{3}{4}\) = \(\dfrac{3\times9}{4\times6}\) = \(\dfrac{27}{36}\)

      \(\dfrac{150}{90}\) = \(\dfrac{150:30}{90:30}\) =  \(\dfrac{5}{3}\) = \(\dfrac{5\times12}{3\times12}\) = \(\dfrac{60}{36}\)

       \(\dfrac{250}{900}\) = \(\dfrac{250:50}{900:50}\) = \(\dfrac{5}{18}\)  = \(\dfrac{5\times2}{18\times2}\) = \(\dfrac{10}{36}\)

Answer 4

Bài 18 Theo bài ra ta có: a = 16k; b = 16n (k; n) =1

     ⇒ 16k + 16n = 128

         16.(k + n) = 128

               k + n = 8

             Vì (k; n) = 1 ⇒ (k; n) = (0; 8); (1; 7); (3; 5)

         ⇒(a; b) = (0; 128); (16; 112); (48; 80)