Đáp án:

1. $\dfrac{30}{235}$ > $\dfrac{168}{1323}$

2. $\dfrac{19}{60}$ < $\dfrac{31}{90}$

3. $\dfrac{15}{23}$ > $\dfrac{70}{117}$

Giải thích các bước giải:

1. $\dfrac{30}{235}$ và $\dfrac{168}{1323}$

$\dfrac{30}{235}$ = $\dfrac{30 * 1323}{235 * 1323}$ = $\dfrac{39690}{310905}$

$\dfrac{168}{1323}$ = $\dfrac{168 * 235}{1323 * 235}$ = $\dfrac{39480}{310905}$

Vì $\dfrac{39690}{310905}$ > $\dfrac{39480}{310905}$ nên $\dfrac{30}{235}$ > $\dfrac{168}{1323}$

2. $\dfrac{19}{60}$ và $\dfrac{31}{90}$

$\dfrac{19}{60}$ = $\dfrac{19 * 90}{60 * 90}$ = $\dfrac{1710}{5400}$

$\dfrac{31}{90}$ = $\dfrac{31 * 60}{90 * 90}$ = $\dfrac{1860}{5400}$

 Vì $\dfrac{1710}{5400}$ < $\dfrac{1860}{5400}$ nên $\dfrac{19}{60}$ < $\dfrac{31}{90}$

3. $\dfrac{15}{23}$ và $\dfrac{70}{117}$

$\dfrac{15}{23}$ = $\dfrac{15 * 117}{23 * 117}$ = $\dfrac{1755}{2691}$

$\dfrac{70}{117}$ = $\dfrac{70 * 23}{117 * 23}$ = $\dfrac{1610}{2691}$

Vì $\dfrac{1755}{2691}$ > $\dfrac{1610}{2691}$ nên $\dfrac{15}{23}$ > $\dfrac{70}{117}$

$\frac{30}{235}$ lớn hơn $\frac{168}{1323}$ 

$\frac{19}{60}$ nhỏ hơn $\frac{31}{90}$ 

$\frac{15}{23}$ lớn hơn$\frac{70}{117}$