Examine the following matchsticks patterns;

If the pattern comtinues, how many matchsticks are needed in the $15$th stage?

If an operator $\oplus$is defined as;

$4\oplus 3=4+5+6$

Then, what is the value of $n\oplus 8$?

The solid as shown in figure is made up of cubical blocks each of side $1$$cm$. The number of blocks is;

Look at the following pattern

$\left(9-1\right)÷8=1$

$\left(98-2\right)÷8=12$

$\left(987-3\right)÷8=123$

$\left(9876-4\right)÷8=1234$

According to this pattern, $\left(987654-6\right)÷8$ is;

Find the number of triangles in the given figure.

Study the following pattern $9 \times 9 = 81, 99 \times 99 = 9801, 999 \times 999 = 998001$............. What is $99999 \times 99999?$

In the figure, $\angle$$ABD$ and $\angle$$CBD$ are mutually: