You are interested in determining how long it will take an investment of €10,000,000 to double in value. The current interest rate is 7 percent compounded annually. How many years will it take €10,000,000 to double to €20,000,000?

So I basicly do:

PV = 10.000.000 // FV = 20.000.000 CHS // r = 7 // and ask my HP12C for N than I get 11

But the answer in the book is 10,24, what is happening? The result looks right to me, how its not 11 in the book?

ps: is the question example 19 in TVM, page 343, can somebody help, please?