### Comment:
10 right? 9 would get you to 512 so you'd need to go one more to get it. Not that it matters just wondering.

### REPLY:
1.7 x 2 = 3.4.       
 3.4 x 2 = 6.8.    
 6.8 x 2 = 13.6.      
 ... x 2 = 27.2.    
 ... x 2 = 54.4.    
 ...x 2 = 108.8.    
 ... x 2 = 217.6.      
 ... x 2 = 435.2.    
 ... x 2 = 870.4.     
 ... x 2 = 1,740.8.       
        
 Yup, looks like you're right. Nine gets him close; ten gets him well past $1B. Cheers.

### END.