Answer:
45.88 seconds
Step-by-step explanation:
[tex]t_1[/tex] = Time taken to sing the fist time = [tex]48.7\ \text{s}[/tex]
Time taken to sing the second time was [tex]2.9\ \text{s}[/tex] less than the first time so
[tex]t_2=t_1-2.9\\\Rightarrow t_2=48.7-2.9\\\Rightarrow t_2=45.8\ \text{s}[/tex]
Time taken to sing the third time was [tex]0.47\ \text{s}[/tex] less than the the second time
[tex]t_3=t_2-0.47\\\Rightarrow t_3=45.8-0.47\\\Rightarrow t_3=45.88\ \text{s}[/tex]
So the time it took the choir to sing the third time was 45.88 seconds.