How long will it take for a $3000 savings account to double its value at a simple interest rate of 10%?

Given P=$3000
           R=10%
And double of P means A=$6000
Now , we know that 
                      A = P×R×t÷100
                      6000=3000×10×t÷100
                      6000×100÷30000 =t
                                  20=t
The Answer is 20 Yrs if rate was for year

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