Quantitative Aptitude - Arithmetic Ability Questions

In the following question, select the odd word pair from the given alternatives.

What is the value of (cosec30 - 1/√3)?

PQR is an equilateral triangle whose side is 10 cm. What is the value (in cm) of the inradius of triangle PQR?

The ratio of spirit and water in the two vessels is 5 : 1 and 3 : 7 respectively. In what ratio the liquid of both the vessels should be mixed such that a new mixture containing half spirit and half water is obtained?

The average marks obtained by a group of 16 students was 20. One student left the group as a result of which the average of the remaining students rose to 21. But another student joined, as a result of which the average marks of the group dropped a bit and became 20.5. What was the average marks obtained by the student who left and the one who joined?

If the numbers  93, 204, 256 are arranged in ascending order, then the right arrangement is 

A batsman in his 12th innings makes a score of 120, and thereby increase his average by 5. The average score after 12th innings is

A can do a piece of work in 9 days while B can do it in 12 days. A and B together can do the work in