Question

The ratio of boys to girls in a class is $7:5$. If there are 42 boys, how many girls are there?

• A. 25
• B. 30
• C. 35
• D. 40

Hint:

To solve ratio problems quickly, ask: "What did I multiply the ratio number by to get the real number?" Since $7 \times 6 = 42$, just multiply the other side of the ratio by the same number: $5 \times 6 = 30$.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
A ratio compares two quantities. If the ratio of boys to girls is $7:5$, it means for every $7$ boys, there are $5$ girls.

Step 2: Key Formula or Approach:
Let the number of boys be $7x$ and the number of girls be $5x$, where $x$ is a common multiplier.

Step 3: Calculation:
1. We are given the number of boys is 42. So: \[ 7x = 42 \] \[ x = \frac{42}{7} = 6 \] 2. Now, find the number of girls using the value of $x$: \[ \text{Girls} = 5x = 5 \times 6 = 30 \]

Step 4: Final Answer:
There are 30 girls in the class.