Question 985702
After 10 min, you are both 3.0 km from your house.
 You are now driving at 70 km/h , and you continue at this constant speed; your brother is going faster than this.
 After another 18 min , your brother arrives at the lake, but you are still 7.0 km away.
:
a) how far is it from your house to the lake?
convert 18 min to hrs: 18/60 = .3 hrs
d = 3 + .3(70) + 7
d = 3 + 21 + 7
d = 31 km to the lake
:
b) what is your brother's average speed?
It took him 18 min to travel 31-3 = 28 km
18 min to hrs:  18/60 = .3 hrs
s = {{{28/.3}}}
s = 93{{{1/3}}} km/hr from the 3 km point
:
c) your brother beats you to the lake by what time?
Your time for the last 28 km
t = {{{28/70}}}
t = .4 hrs which is .4(60) = 24 min
24 - 18 = 6 min, beat you by this time