Question

The perimeter of a rectangular metal plate is 15 cm. Find the length of the rectangular plate (in decimals) whose width is 228 cm. Use estimation in tenths place.

Answer 1

The Solution.

Representing the problem in a diagram, we have

By formula,

$P=2(L+W)$

In this case,

$P=15\operatorname{cm},L=?,W=\frac{22}{8}cm$

Substituting these values in the formula above, we get

$15=2(L+\frac{22}{8})$

Clearing the bracket, we get

$15=2L+(2\times\frac{22}{8})$$\begin{gathered} 15=2L+\frac{11}{2} \\ \\ 15=2L+5.5 \end{gathered}$$\begin{gathered} 15-5.5=2L \\ 9.5=2L \end{gathered}$

Dividing both sides by 2, we get

$L=\frac{9.5}{2}=4.75\approx4.8\operatorname{cm}$

Therefore, the correct answer is option C.