Five years ago, the average age of four girls, was 7 years. A new girl is included then the average present age becomes 13 years. The present age of the new girl is:
Five years ago, the average age of four girls = 7
Sum of the ages of the four girls = 7$$\times\ $$4= 28Â
Sum of the present ages of four girls = 28+20= 48
Let the present age of new girl = $$x$$
Average of the present ages of five girls = 13
$$=$$> Â Â Â $$\ \frac{\ 48+x}{5}=13$$Â Â Â Â Â Â
          $$\ \ x=65-48=17$$        Â
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