Let the quantity of the tea that is
Rs. 62 per kg be
x kg and that of tea that is
Rs. 72 per kg be
y kg.
Hence, the required ratio is x:y.
Price of x kg tea =Rs. 62x
Price of y kg tea =Rs. 72y
If we mix both varieties of tea, the quantity of the mixture will be x+y.
Now, this mixture is Rs. 64.50 per kg.
Hence, the total price of mixture =Rs. 64.50(x+y)
So, 62x+72y=64.50(x+y)
⇒62x+72y=64.5x+64.5y
⇒64.5x−62x=72y−64.5y
⇒2.5x=7.5y
So, x:y=3:1
Hence, the required ratio is 3:1.