Verified answer

Let consumption be C and unit price be P.

Then total cost is P * C = PC

Increase price by 10% to get new P = 1.1P

New total cost is 1.1P * Q = PC

where Q is the new consumption

=> Q = C/1.1 = 0.91C

Consumption must therefore be reduced by 0.09 or 9%

She can now consume (100/110)% of the previous. Or 90.9% of previous consumption.

This will be a reduction of 9.1%;