Tính bằng cách thuận tiện:     517 × 1 652 – 517 × 652

    517 × 1 652 – 517 × 652

= 517 × (1 652 – 652)

= 517 × 1 000

= 517 000

   \(\frac{{14}}{{11}}\) × \(\frac{7}{2}\) × \(\frac{{11}}{7}\)

= \(\left( {\frac{{14}}{{11}} \times \frac{{11}}{7}} \right)\) × \(\frac{7}{2}\)

= 2 × \(\frac{7}{2}\)

= 7