1. Over the summer, the price of a one-bedroom apartment increased by $21 \%$, a two-bedroom apartment by $11 \%$, and the total cost of the apartments by $15 \%$. How many times cheaper is the one-bedroom apartment compared to the two-bedroom apartment?
Answer. One and a half times.

Solution. Let the cost of a one-bedroom apartment be $a$ rubles, and a two-bedroom apartment be $b$ rubles. Then, from the condition of the problem, it follows that $1.21 a + 1.11 b = 1.15(a + b)$, from which $1.5 a = b$.

## Grading Criteria.

- Any complete correct solution - 7 points.
- The correct equation with two variables is obtained, but incorrect or no conclusions are drawn from the equation, - 3 points.
- A solution in which specific prices of apartments are considered, - 2 points.
- Only the correct answer - 0 points.