goodwill is assigned to one or more reporting segments on the date of acquisition . we evaluate goodwill for impairment by comparing the fair value of each of our reporting segments to its carrying value , including the associated goodwill . to determine the fair values , we use the market approach based on comparable publicly traded companies in similar lines of businesses and the income approach based on estimated discounted future cash flows . our cash flow assumptions consider historical and forecasted revenue , operating costs and other relevant factors . we amortize intangible assets with finite lives over their estimated useful lives and review them for impairment whenever an impairment indicator exists . we continually monitor events and changes in circumstances that could indicate carrying amounts of our long-lived assets , including our intangible assets may not be recoverable . when such events or changes in circumstances occur , we assess recoverability by determining whether the carrying value of such assets will be recovered through the undiscounted expected future cash flows . if the future undiscounted cash flows are less than the carrying amount of these assets , we recognize an impairment loss based on any excess of the carrying amount over the fair value of the assets . we did not recognize any intangible asset impairment charges in fiscal 2012 , 2011 or 2010 . our intangible assets are amortized over their estimated useful lives of 1 to 13 years . amortization is based on the pattern in which the economic benefits of the intangible asset will be consumed . the weighted average useful lives of our intangible assets was as follows : weighted average useful life ( years ) .

weighted averageuseful life ( years ): purchased technology: 5
customer contracts and relationships: 10
trademarks: 7
acquired rights to use technology: 9
localization: 1
other intangibles: 3

software development costs capitalization of software development costs for software to be sold , leased , or otherwise marketed begins upon the establishment of technological feasibility , which is generally the completion of a working prototype that has been certified as having no critical bugs and is a release candidate . amortization begins once the software is ready for its intended use , generally based on the pattern in which the economic benefits will be consumed . to date , software development costs incurred between completion of a working prototype and general availability of the related product have not been material . internal use software we capitalize costs associated with customized internal-use software systems that have reached the application development stage . such capitalized costs include external direct costs utilized in developing or obtaining the applications and payroll and payroll-related expenses for employees , who are directly associated with the development of the applications . capitalization of such costs begins when the preliminary project stage is complete and ceases at the point in which the project is substantially complete and is ready for its intended purpose . income taxes we use the asset and liability method of accounting for income taxes . under this method , income tax expense is recognized for the amount of taxes payable or refundable for the current year . in addition , deferred tax assets and liabilities are recognized for expected future tax consequences of temporary differences between the financial reporting and tax bases of assets and liabilities , and for operating losses and tax credit carryforwards . we record a valuation allowance to reduce deferred tax assets to an amount for which realization is more likely than not . table of contents adobe systems incorporated notes to consolidated financial statements ( continued ) .

Questions:
what is the useful life in years for purchased technology?
what is the life in years for customer contracts and relationships?
what is the sum number of years?
what is the average number of years?

Answers:
5
10
15.0
7.5