Question

Suppose$2kg$ of sugar contains $9\times {10}^6$ crystals. How many sugar crystals are there in $5kg$ of sugar?

Answer 1

Finding the number of sugar crystals in $5kg$ of sugar:

Let us assume that sugar crystals be $x$.

Since the weight of sugar is directly proportional to the number of sugar crystals.

$$\begin{gathered} \frac{2}{9\times {10}^6}=\frac{5}{x} \\ \Rightarrow x=\frac{5\times 9\times {10}^6}{2} \\ \Rightarrow x=\frac{45\times {10}^6}{2} \\ \Rightarrow x=22.5\times {10}^6 \\ \Rightarrow x=22.5\times {10}^6\times \frac{10}{10} \end{gathered}$$

$\Rightarrow x=2.25\times {10}^7$ crystals

Hence, the number of sugar crystals in $5kg$ of sugar is $2.25\times {10}^7$