Respostas

2014-05-29T23:26:35-03:00
30min - 1/2 hora 
15min - 1/4 hora 
20 min - 1/3 hora 

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2014-05-29T23:29:20-03:00
A)
1 hora ----- 60'
x hora ----- 15' =====>>>> x = 15/60 = 1/4 hora
......
b) 
1 hora ----- 60'
x hora ----- 20' =====>>>> x = 20/60 = 1/3 hora
......
c)
1 hora ----- 60'
x hora ----- 30' =====>>>> x = 30/60 = 1/2 hora

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