Answer:
(a) [tex]\dfrac{1}{10}[/tex]
(b) 21 miles
Step-by-step explanation:
(a) From the question,
b = 3a
c = 2b = 2 × 3a = 6a
The total length of the road = a + b + c = a + 3a + 6a = 10a
The fraction of the total length of the roads that is a
= [tex]\dfrac{a}{a+b+c} = \dfrac{a}{10a} = \dfrac{1}{10}[/tex]
(b) If b is 7 miles longer than a, then
b - a = 7
3a - a = 7
2a = 7
a = 3.5
c = 6a = 6 × 3.5 = 21 miles
