At the end of a business conference, the ten people present all shake hands with each other once. How many handshakes will there be altogether?
90
For each handshake, two people shake hands. The total number of handshakes can be found using the formula for combinations \( C(n, 2) \), where \( n \) is the number of people: \[ C(10, 2) = \frac{10 \times 9}{2} = 45. \] Thus, the total number of handshakes is 45. So, the correct answer is (b) 45.
In a special racing event, the person who enclosed the maximum area would be the winner and would get ₹ 100 every square metre of area covered by him/her. Jonsson, who successfully completed the race and was the eventual winner, enclosed the area shown in the figure below. What is the prize money won?
\(\textit{Note: The arc from C to D makes a complete semi-circle. Given: }\) $AB=3$ m, $BC=10$ m, $CD=BE=2$ m.

A lawn is in the form of an isosceles triangle. The cost of turfing on it came to $₹ 1{,}200$ at ₹ 4 per m$^2$. If the base be 40 m long, find the length of each side.
Nine squares are chosen at random on a chessboard. What is the probability that they form a square of size $3\times 3$?
$A,B,C,D$ are four towns, any three of which are non-colinear. In how many ways can we construct three roads (each road joins a pair of towns) so that the roads do not form a triangle?