Question

The weight of a piece of wire is directly proportional to its length. A piece of wire is 25 cm long and has a weight of 6 grams. Another piece of the same wire is 30 cm long. Calculate the weight of the 30 cm piece of wire.

• A. 6.4 grams
• B. 7.2 grams
• C. 8.6 grams
• D. 9 grams

Answer 1

The correct option is B 7.2 grams

$\begin{array}{ccc}\text{Weight}& 6g& ?\\ \text{Length (in cm)}& 25& 30\end{array}$

Given that the weight of a piece of wire is directly proportional to its length.

The ration of weight and length will be constant.

$\frac{Weight}{Length}=Constant$

$\Rightarrow \frac{25}{6}=\frac{30}{x}$

$\Rightarrow x=30\times \frac{6}{25}$
$\therefore x=7.2$ grams.