34. 5 ga karrali ikki xonali sonlar nechta?

We need to find the number of two-digit numbers that are multiples of 5.

Two-digit numbers range from 10 to 99.

The two-digit multiples of 5 are:

• 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95.

To count them, we can use the formula for an arithmetic sequence:

Last term = First term + (n - 1) * common difference

Here, the first term is 10, the last term is 95, and the common difference is 5.

\( 95 = 10 + (n - 1) \times 5 \)

\( 95 - 10 = (n - 1) \times 5 \)

\( 85 = (n - 1) \times 5 \)

\( \frac{85}{5} = n - 1 \)

\( 17 = n - 1 \)

\( n = 17 + 1 \)

\( n = 18 \)

So, there are 18 two-digit numbers that are multiples of 5.

Ответ: 18