Sequences and S...

On the eve of Diwali festival, a group of 12 friends greeted every other friend by sending greeting cards. Find the number of cards purchased by the group. 

In a class there are 18 boys who are over 160 cm tall If these constitute three-fourths of the boys and the total number of boys is tow-third of the total number of students in the class what is the number of girls in the class?

Out of 100 students 50 fail in English and 30 in Maths. If 12 students fail in both English and Maths, then the number of students passing both the subjects is

If the area of the triangle formed by the points $$(-2,3), (4,-5)$$ and $$(-3,y)$$ is 10 square units then $$y =$$

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? 

How many numbers of four digits can be formed from the digits 0, 1, 2, 3, and 4? 

A group of 1200 persons consisting of captains and soldiers is travelling in a train. For every 15 soldiers there is one captain. The number of captains in the group is: 

A car driver knows four different routes from Delhi to Amritsar. From Amritsar to Pathankot, he knows three different routes and from Pathankot to Jammu he knows two different routes. How many routes does he know from Delhi to Jammu?

In a chess tournament each of six players will play every other player exactly once. How many matches will be played during the tournament? 

If the area of the triangle formed by $$ (-2,5), (x,-3) $$ and $$(3,2)$$ is $$14 $$ square units, then $$x=$$ ____.