Answer: a) 5:9:6, b) 380
Step-by-step explanation:
Let the number of participant be 'x'.
Let the number of participant of 3-km route be [tex]\dfrac{x}{4}[/tex]
Let the number of participants of 5-km route be [tex]\dfrac{9x}{20}[/tex]
Let the number of participants of 8-km route be
[tex]x-\dfrac{x}{4}-\dfrac{9x}{20}=\dfrac{20x-5x-9x}{20}=\dfrac{6x}{20}=\dfrac{3x}{10}[/tex]
According to question, we get that
[tex]4(3\times \dfrac{x}{4}+5\times \dfrac{9x}{20}+8\times \dfrac{3x}{10})=8208\\\\\dfrac{3x}{4}+\dfrac{9x}{4}+\dfrac{24x}{10}=2052\\\\\dfrac{15x+45x+48x}{20}=2052\\\\108x=2052\times 20=41040\\\\x=\dfrac{41040}{108}\\\\x=380[/tex]
Therefore, the number of participants is 380.
Number of participants of 3 km route [tex]\dfrac{380}{4}=95[/tex]
Number of participants of 5 km route [tex]\dfrac{380\times 9}{20}=171[/tex]
Number of participants of 8 km route [tex]\dfrac{380\times 3}{10}=114[/tex]
Ratio of the number of participants completed 3 km to 5 km to 8 km is given by
95:171:114
=5:9:6
Hence, a) 5:9:6, b) 380