Bài 1.

Ta có :$\dfrac{1}{2}$ > $\dfrac{2}{5}$ > $\dfrac{1}{3}$

Nên : Hoa ăn ít bánh nhất

An ăn ít bánh nhất.

Bài 2

a,$\dfrac{2}{4}$ < $\dfrac{3}{4}$

b,$\dfrac{1}{5}$ < $\dfrac{2}{5}$ < 1

c,$\dfrac{4}{14}$ = $\dfrac{6}{21}$ = $\dfrac{2}{7}$

Bài 3

a,$\dfrac{3}{8}$ < $\dfrac{5}{9}$

$\dfrac{3 × 9}{8 × 9}$ = $\dfrac{27}{72}$

$\dfrac{5 × 9}{8 × 9}$ = $\dfrac{40}{72}$

b,$\dfrac{4}{5}$ > $\dfrac{3}{8}$

$\dfrac{4 × 8}{5 × 8}$ = $\dfrac{32}{40}$

$\dfrac{3 × 5}{8 × 5}$ = $\dfrac{15}{40}$

c,$\dfrac{7}{3}$ > $\dfrac{8}{6}$

$\dfrac{7 × 6}{3 × 6}$ = $\dfrac{42}{18}$

$\dfrac{8 × 3}{6 × 3}$ = $\dfrac{24}{18}$

d,$\dfrac{9}{3}$ = $\dfrac{12}{4}$

$\dfrac{9 × 4}{3 × 4}$ = $\dfrac{36}{12}$

e,$\dfrac{7}{8}$ < $\dfrac{8}{9}$

$\dfrac{7 × 9}{8 × 9}$ = $\dfrac{63}{72}$

$\dfrac{8 × 8}{9 × 8}$ = $\dfrac{64}{72}$

g,$\dfrac{5}{4}$ > $\dfrac{6}{5}$ > $\dfrac{7}{6}$

$\dfrac{5 × 15}{4 × 15}$ = $\dfrac{75}{60}$

$\dfrac{6 × 12}{5 × 12}$ = $\dfrac{72}{60}$

$\dfrac{7 × 10 }{6 × 10}$ = $\dfrac{70}{60}$

$#anhvu19120122#$
#$BTS$

Bài 1:

Ta có: $\frac{1}{3}$=$\frac{10}{30}$

    và: $\frac{2}{5}$=$\frac{12}{30}$

    có: $\frac{1}{2}$=$\frac{15}{30}$

Vì: $\frac{10}{30}$<$\frac{12}{30}$<$\frac{15}{30}$ nên $\frac{1}{3}$<$\frac{2}{5}$<$\frac{1}{2}$

Vậy: Hoa ăn nhiều nhất, An ăn ít nhất.

Bài 2:

a.$\frac{x}{4}$<$\frac{3}{4}$

⇒x=2;1;0

b.$\frac{1}{5}$<$\frac{y}{5}$$\frac{1}{3}$<1

⇒x=2;3;4

c.$\frac{4}{x}$=$\frac{y}{21}$=$\frac{2}{7}$

Ta có: $\frac{4}{x}$=$\frac{2}{7}$⇒x=14

    và: $\frac{y}{21}$=$\frac{2}{7}$⇒y=6

Bài 3:

a.$\frac{3}{8}$<$\frac{5}{9}$ 

b.$\frac{4}{5}$>$\frac{6}{12}$ 

c.$\frac{7}{3}$>$\frac{8}{6}$ 

d.$\frac{9}{3}$=$\frac{12}{4}$ 

e.$\frac{7}{8}$<$\frac{8}{9}$ 

f.\frac{5}{4}$>$\frac{6}{5}$>$\frac{7}{6}$