# CHAPTER 18 REVIEW EXERCISES

# CONCEPT CHECK EXERCISES

Determine each of the following as being either ** true** or

**If it is false, explain why.**

*false*.The ratio of 25 cm to 50 mm is 5.

If 20 m is divided into two parts in the ratio of 3/2, the parts are 14 m and 6 m.

If

`y`varies inversely as the square of`x`, and $y\hspace{0.17em}=\hspace{0.17em}4$ when $x\hspace{0.17em}=\hspace{0.17em}\mathrm{1/4}\hspace{0.17em},\hspace{0.17em}$ then $y\hspace{0.17em}=\hspace{0.17em}4\hspace{0.17em}/\hspace{0.17em}{x}^{2}\hspace{0.17em}.\hspace{0.17em}$If

`R`varies jointly with`s`and the square of`t`, and inversely as the square of`r`, then $k\hspace{0.17em}=\hspace{0.17em}\left({\displaystyle \frac{R}{s}}\right){\left({\displaystyle \frac{r}{t}}\right)}^{2}\hspace{0.17em}.\hspace{0.17em}$

# PRACTICE AND APPLICATIONS

In Exercises 5–18, find the indicated ratios.

840 mg to 3g

300 nm to $6\mu \text{m}$

375 mL to 25 cL

12 ks to 2 h

The number $\pi $ equals the ratio of the circumference

`c`of a circle to its diameter`d`. To check the value of $\pi \hspace{0.17em},\hspace{0.17em}$ a technician used computer simulation to measure the circumference ...

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