Geeta has saved Rs. 300 and Meeta has saved Rs. 450. Together, they have a total of Rs. (300 + 450) = Rs. 750.

They each spend half of their money on a trip to the mall, so Geeta spends Rs. 300/2 = Rs. 150 and Meeta spends Rs. 450/2 = Rs. 225.

After their trip to the mall, Geeta has Rs. 300 – 150 = Rs. 150 left, and Meeta has Rs. 450 – 225 = Rs. 225 left.

If they combine their remaining money, they have Rs. (150 + 225) = Rs. 375.

To buy the Barbie doll, they need Rs. 660 – 375 = Rs. 285 more.