Răspuns:
Aplici regula de 3 simpla
60 oscilatii-----------------30s
10 ocilatii -------------------x
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60/10=30/x
6/1=30/x
6x=30
x=30/6=5 sec
b.APLICI IN CONTINUARE regula de 3 simpla
60----------------30s
x--------------------20s
______________________________________
60/x=30/20
60/x=3/2
60*2=3x
120=3x
x=120/3
x=40 oscilatii
Explicație: