Chapter 6.5, Problem 29PPS

To determine

To write a proportion and solve for unknown variable in

20 boxes on 4 shelves

b boxes in 20 shelves

Answer to Problem 29PPS

20

Explanation of Solution

Given:

20 boxes on 4 shelves

b boxes in 20 shelves

Calculation:

Writing a proportion,

  $\begin{array}{l}\Rightarrow \frac{20\text{boxes}}{b\text{boxes}}=\frac{4\text{shelves}}{20\text{shelves}}\\ \Rightarrow \frac{20}{b}=\frac{4}{20}\\ \Rightarrow 20\times 4=4\times b[\because \text{Performing cross multiplication}]\\ \Rightarrow 80=4b\\ \Rightarrow 4b=80\\ \Rightarrow b=\frac{80}{4}\\ \Rightarrow b=20\end{array}$

Conclusion:

Therefore, the value of b is equal to 20.