Cement and sand were mixed in the ratio \( 2: 5 \). How many kilograms of cement was contained in the 35 kg of the mixture? A. \( \quad 10 \mathrm{~kg} \)

To find the amount of cement in the mixture, first, we need to determine the total parts of the mixture. The ratio of cement to sand is \( 2:5 \), which adds up to \( 2 + 5 = 7 \) parts. In a \( 35 \) kg mixture, the fraction of the mixture that is cement is \( \frac{2}{7} \). Therefore, the weight of the cement is \( \frac{2}{7} \times 35 = 10 \) kg. So, the answer \( A. \ 10 \text{ kg} \) is correct! In the construction world, understanding material ratios is crucial. For example, when creating concrete, the cement-to-sand ratio can affect the mixture's strength and workability. Knowing how to calculate the proportions accurately ensures the final product meets the required standards for durability and stability. Remember, a little math goes a long way in building strong structures!