KSA Grade 7 Ratios and Proportional Relationships. Practice it free.

The scale factor from $\triangle RST$ to $\triangle UVW$ is $\dfrac{42}{28} = \dfrac{3}{2}\textsf{.}$ So $UV = 10 \cdot \dfrac{3}{2} = 15\textsf{.}$

Discount: $\dfrac{40}{100} \times \text{\char36}30 = \text{\char36}12\textsf{.}$ Sale price: $\text{\char36}30 - \text{\char36}12 = \text{\char36}18\textsf{.}$

Discount: $\frac{25}{100} \times \text{\char36}200 = \text{\char36}50$. Sale: $\text{\char36}200 - \text{\char36}50 = \text{\char36}150$.

Increase $= 13{,}800 - 12{,}000 = 1{,}800$. Percent increase $= \dfrac{1{,}800}{12{,}000} = 0.15 = 15\%$.

Tax: $\dfrac{10}{100} \times \text{\char36}60 = \text{\char36}6\textsf{.}$

Tip: $\dfrac{15}{100} \times \text{\char36}80 = \text{\char36}12\textsf{.}$ Total: $\text{\char36}80 + \text{\char36}12 = \text{\char36}92\textsf{.}$

$I = 100 \times 0.05 \times 1 = \$5$.

Book: $40+0.05\cdot 40=42\textsf{.}$ Headphones: $60+0.08\cdot 60=64.80\textsf{.}$ Cable: $20+0.10\cdot 20=22\textsf{.}$ Total: $42+64.80+22=\text{\char36}128.80\textsf{.}$