1. **State the problem:** We know that 50% of the children in the sports club go swimming, and 50% of those who swim also dive. We are told that 5 children both swim and dive. We need to find the total number of children in the sports club. 2. **Define variables:** Let the total number of children in the club be $N$. 3. **Use the given percentages:** - Number of children who swim = 50% of $N$ = $0.5N$ - Number of children who swim and dive = 50% of those who swim = $0.5 \times 0.5N = 0.25N$ 4. **Set up the equation:** We know the number of children who swim and dive is 5, so $$0.25N = 5$$ 5. **Solve for $N$:** $$N = \frac{5}{0.25} = 20$$ 6. **Interpretation:** There are 20 children in the sports club. This matches the given answer and confirms the method.