1 Thực hiện phép tính: A 1/4 + 3/4 cdot 2/3 - 0,5 b 13/25 — Không quảng cáo

Phương pháp giải

Áp dụng quy tắc cộng, trừ, nhân, chia.

1)

a) $\frac{1}{4} + \frac{3}{4} \cdot \left( {\frac{2}{3} - 0,5} \right)$$= \frac{1}{4} + \frac{3}{4} \cdot \left( {\frac{2}{3} - \frac{1}{2}} \right)$$= \frac{1}{4} + \frac{3}{4} \cdot \frac{1}{6}$$= \frac{1}{4} + \frac{1}{8}$$= \frac{3}{8}$

b) $1\frac{3}{{25}} - \frac{{17}}{{19}} - \frac{3}{{25}} + \frac{{2022}}{{2023}} - \frac{2}{{19}}$$= \left( {1\frac{3}{{25}} - \frac{3}{{25}}} \right) + \left( {\frac{{ - 17}}{{19}} + \frac{{ - 2}}{{19}}} \right) + \frac{{2022}}{{2023}}$ $= 1 + ( - 1) + \frac{{2022}}{{2023}}$ $= \frac{{2022}}{{2023}}.$

2)

a) $\frac{2}{3}x - \frac{1}{2} = \frac{1}{{10}}$

$\frac{2}{3}x = \frac{1}{{10}} + \frac{1}{2}$

$\frac{2}{3}x = \frac{3}{5}$

$x = \frac{3}{5}:\frac{2}{3}$

$x = \frac{3}{5}:\frac{2}{3}$

$x = \frac{9}{{10}}$

Vậy $x = \frac{9}{{10}}$.

b) $5,16 - 2x = (5,7 + 2,3) \cdot ( - 0,3)$

$5,16 - 2x =  - 2,4$

$2x = 5,16 - ( - 2,4)$

$2x = 7,56$

$x = 7,56:2$

$x = 3,78$

Vậy $x = 3,78$