A new treatment for a specific type of cancer is found to reduce metastatic spread of the tumor. For the existing treatment, metastatic spread occurs...

A new treatment for a specific type of cancer is found to reduce metastatic spread of the tumor. For

the existing treatment, metastatic spread occurs in 20% of patients. In the new treatment,

metastatic spread occurs in 10% of patients. How many patients must be treated to reduce one new

case of metastatic spread of the tumor?