Hello there. To solve this question, we'll have to remember some properties about inversely proportional terms.
Let's start labeling the terms:
Say Current is given by I, Resistance is given by R and voltage is given by V.
By Ohm's Law, we know that:
[tex]V=R\cdot I[/tex]In fact, this is the definition we need to find the answer.
But, to understand why the question mention the fact that they are inversely proportional, note:
We say two numbers x and y are inversely proportional when:
[tex]x\cdot y=k[/tex]Their product is equal to a constant. k is the constant (of proportionality).
Now, using the given values in the question, we can solve this question.
If the current is 30 ampère when the resistance is 5 ohms, we have to find the current when the resistance is 7.8 ohms.
First scenery:
[tex]V=30\cdot5[/tex]Multiply the numbers
[tex]V=150[/tex]Second scenery:
[tex]V=7.8\cdot I[/tex]Plugging V = 150, we get:
[tex]150=7.8\cdot I[/tex]Divide both sides of the equation by a factor of 7.8
[tex]I=\frac{150}{7.8}[/tex]Simplify the fraction by a factor of 2
[tex]I=\frac{75}{3.9}[/tex]Using a calculator, we get the following approximation
[tex]I\approx19.2\text{ A}[/tex]A is for Ampère.