Answer: Price of cereals must fall by 12%
Step-by-step explanation:
A 10% rise in the price of milk will lead to a fall in quantity demanded by =-0.9 * 10= 9%.
To prevent the demand for cereals from falling by 9%, the price of cereals must fall by
![E = (Percentage change in Qd)/(Percentage change in price)](https://img.qammunity.org/2019/formulas/business/college/7gh4o8xjbul18qmkb598gcz1xq56xygj80.png)
![Percentage change in price = (Percentage change in Qd)/(e)](https://img.qammunity.org/2019/formulas/business/college/vqrpaxuo0794nynx4drgzhcwc25cy8rfj3.png)
![Percentage change in price = (9)/(-0.75)](https://img.qammunity.org/2019/formulas/business/college/z6c4efeywkk0xs539b7ajrdcyp4l810p5p.png)
![Percentage change in price = -12%](https://img.qammunity.org/2019/formulas/business/college/rlf44rbaxa0ovhtvajl1pwhs9rwbuyqmvh.png)
Thus, to offset the effect of a 10% rise in price of milk, the price of cereals must fall by 12%.