Quantitative Aptitude - Arithmetic Ability Questions

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

If α + β = 90° and α:β = 2:1, then the ratio of cosα to cosβ is

What is the value of (1+cosA)/(1-­cosA)?

The reciprocal of the sum of the reciprocals of 8/7 and 5/6 is:

The first and last terms of an arithmetic progression are 23 and ­42. What is the sum of the series if it has 14 terms?

Mr. Raghav taught Geometry for 36 hours. If the time taken in teaching Ratio consitutes one-fourth of the time for Arithmetic, then for how much time (in hours) did he taught the topic of Ratio?

A vendor buys 12 bananas for Rs 60 and sells 5 bananas for Rs 32. What will be his gain (in %)?

The difference between cost price and selling price is Rs 494. If loss percentage is 19%, then what is the selling price (in Rs)?