4. The length and width of a rectangular prism are 20 cm and 15 cm, respectively. If the numerical value of its volume is equal to the numerical value of its surface area, then its height is $\qquad$ cm (write the answer as an improper fraction)

The length and width of a rectangular prism are 20 cm and 15 cm, respectively. If the numerical value of its volume is equal to the numerical value of its surface area, then its height is $\qquad$ cm (write the answer as an improper fraction)
【Answer】 $\frac{60}{23}$ Analysis: Let the height be $\mathrm{h}$, then $20 \times 15 \times \mathrm{h}=(20 \times 15+20 \mathrm{~h}+15 \mathrm{~h}) \times 2$, thus $\mathrm{h}=\frac{60}{23}$