3.11 Apples of the first grade for a total of 228 rubles and apples of the second grade for a total of 180 rubles were delivered to the store. During unloading, the delivered apples were accidentally mixed. It was found that if all the apples are now sold at one price - 90 kopecks lower than the price per kilogram of first-grade apples, the planned amount will be received. How many kilograms of apples were delivered, if it is known that there were 5 kg more of second-grade apples than first-grade apples?

## Ratios between natural numbers
3.11 Let's construct the following table:

| Apple Variety | Cost, rub | Quantity, tons | Price, rub/kg |
| :---: | :---: | :---: | :---: |
| First | 228 | $x$ | $\frac{228}{x}$ |
| Second | 180 | $x+5$ | $\frac{180}{x+5}$ |

According to the problem, we have the equation

$\left(\frac{228}{x}-0.9\right)(2 x+5)=408$,

from which, after transformations, we arrive at the quadratic equation

$$
6 x^{2}-145 x-3800=0
$$

We find its roots:

$x_{1}=\frac{145+335}{12}=40, x_{2}=\frac{145-335}{12}<0$ (not suitable).

Thus, 40 tons of the first variety of apples and 45 tons of the second variety of apples were delivered, i.e., a total of 85 tons.

Answer: 85 tons.