Respuesta :

multiplying ratios is just like multiplying fractions. 

Ex: 

5:10 = 5/10 

5:10 · 2:20 = 5/10·2/20. 

keep 5/10, 
simplify 2/20 to 1/10, 
multiply 5·1, and 10·10, and the answer is 5/100 or .05