1 Вправа 1Алгебра 8 клас Тарасенкова 2025 · Розділ 1 · стор. 5

1. Обчисліть найбільш раціональним способом.

Спільний:

1) ${\displaystyle 2,71\cdot 9,2+9,2\cdot 3,29=}$${\displaystyle 9,2\cdot (2,71+3,29)=}$${\displaystyle 9,2\cdot 6=}$${\displaystyle 55,2}$;

2) ${\displaystyle 15,68\cdot 3,1-13,58\cdot 3,1=}$${\displaystyle 3,1\cdot (15,68-13,58)=}$${\displaystyle 3,1\cdot 2,1=}$${\displaystyle 6,51}$;

3) ${\displaystyle 28\cdot 5,7\cdot \frac{3}{14}=}$${\displaystyle \frac{28\cdot 3}{14}\cdot 5,7=}$${\displaystyle \frac{2\cdot \cancel{14}\cdot 3}{\cancel{14}}\cdot 5,7=}$${\displaystyle 6\cdot 5,7=}$${\displaystyle 34,2}$;

4) ${\displaystyle 2\frac{5}{7}-11\frac{2}{5}+19\frac{2}{7}-2\frac{3}{5}=}$${\displaystyle \left(2\frac{5}{7}+19\frac{2}{7}\right)-\left(11\frac{2}{5}+2\frac{3}{5}\right)=}$${\displaystyle 22-14=}$${\displaystyle 8}$;

5) ${\displaystyle (6\frac{2}{3}-\frac{1}{4})\cdot 24=}$${\displaystyle 6\frac{2}{3}\cdot 24-\frac{1}{4}\cdot 24=}$${\displaystyle \frac{20}{3}\cdot 24-\frac{24}{4}=}$${\displaystyle \frac{20\cdot 8\cdot \stackrel{1}{\cancel{3}}}{\underset{1}{\cancel{3}}}-\frac{6\cdot \stackrel{1}{\cancel{4}}}{\underset{1}{\cancel{4}}}=}$${\displaystyle 160-6=}$${\displaystyle 154}$;

6) ${\displaystyle 17\frac{5}{13}\cdot 7\frac{1}{3}+2\frac{8}{13}\cdot 7\frac{1}{3}=}$${\displaystyle 7\frac{1}{3}\cdot (17\frac{5}{13}+2\frac{8}{13})=}$${\displaystyle 7\frac{1}{3}\cdot 20=}$${\displaystyle \frac{22}{3}\cdot 20=}$${\displaystyle \frac{440}{3}=}$${\displaystyle 146\frac{2}{3}}$.