Quantitative Aptitude - Arithmetic Ability Questions

In the following question, four number pairs are given. The number on left side of (–) is related to the number of the right side of (–) with some Logic/Rule/Relation. Three are similar on basis of same Logic/Rule/Relation. Select the odd one out from the given alternatives.

If cos -225° = x, then the value of x is

What is the value of (cot45 - √2) ?

What is the slope of the line parallel to the line passing through the points (-­4,­-6) and (2,­-3)?

What is the difference (in Rs) between the compound interests on Rs. 1000 for 1 year at 10% per annum compounded yearly and half-yearly?

A hexagonal prism has 18 edges. How many vertices does it have?

Calculate the simple interest if Rs. 1800 is invested for 10 years at a rate of 5% per annum.

A sum of money invested at simple interest becomes 13/10 of itself in 2 years and 6 months. What is the rate (in percentage) of interest per annum?