You start with 100%, add 80% for the increase and you get 180%, take away 40% for the decrease and you get 140%
Use the tangent-chord theorem:
The included chord-tangent angle is half the size of the intercepted arc.
The intercepted arc is "c".
The included chord-tangent-angle is the supplement of 110=70 degrees.
Therefore from the tangent-chord theorem, 70 degrees = half the size of arc "c"
=>
arc "c" = 2*intercepted angle = 2*70 degrees = 140 degrees.
We need to write the following expression and solve for x:
9/18 = 100/x
So: 9x = 1800
x = 200
So it would take him 200 minutes to deliver 100 papers.
We do the same for 72 papers
9/18 = 72/x
so 9x = 1296
and x = 144
It would take him 144 minutes to deliver 72 papers.
We'll take out LCM of 24 seconds and 28 seconds.
that is, 168 seconds.
That means,
Car A and Car B will be side by side to each other after 2 mins 48 seconds after start.