A Man Earns ₹20 on First Day. How soon will he have ₹60 in Hand ?

A man earns ₹20 on first day.
He spends ₹15 on 2nd day.
He again earns ₹20 on 3rd day and spends ₹15 on 4th day.
If he saves like this,
How soon he will have ₹60 in hand??

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By Earning & Spending he would have 40rs on the 16th day inhand.
Then on 17th day he would earn 20rs more making it 60rs on the 17th day