Differentiation...

A man has 9 friends, 4 boys and 5 girls. In how many ways can be invite them, if there have to be exactly three girls in the invites?

Complete the addition square by finding the missing numbers.
Find $$(A-B)-(C-D)$$

The models are shaded to show which of the following?

Fathom is a unit once used by sailors to measure the depth of water. If a sunken ship was located underwater at $$240$$ feet, which expression would describe the location of the ship in fathoms?
$$ { 1\ fathom=6\ feet } $$

Differentiate

The number of ways in which ten candidates $$A_1, A_2,......A_{10}$$ can be ranked such that $$A_1$$ is always above $$A_{10}$$ is

Select a figure from the options which will replace the question mark to complete the given series.

Find $$\dfrac{{dy}}{{dx}}$$ of the following $$y = 1 + 2x + 3{x^2} + \left( {n - 1} \right){x^{n - 2}}$$

Select the missing number from the given matrix:

From a well shuffled pack of $$52$$ playing cards two cards drawn at random. The probability that either both are red or both are kings is: