sherxon
Andy makes a trip to a forest on his bicycle, and Bob does so on his motorcycle. Bob covers one mile 4 minutes faster than Andy does. They both spent two hours on their respective trips. However, Bob covered 40 miles more distance than did Andy. How many miles did Andy cover during his trip?
A. 10
B. 15
C. 20
D. 30
E. 40
I. Use options
Start from the central value and depending on answer can move to lower or higher values.
So A covers 20, => speed = 20/2 or 10mph, that is 1 mile in 60/10 or 6 minutes.
B covers 60 => speed = 60/2 or 30mph , that is 1 mile in 60/30 or 2 minutes, meaning 4 minutes faster than A.
Fits in exactly.
II. Algebraic
Let the time taken per mile By A be x, so by B is x-4
Distance traveled by A in 2 hours = \(\frac{60}{x}*2\)
Distance traveled by B in 2 hours = \(\frac{60}{x-4}*2\)
Thus extra distance traveled by B in 2 hours = \(\frac{120}{x-4}-\frac{120}{x}=40\)
\(120x-120x+480=40x^2-160x…..x^2-4x-12=0\)
\(x^2-6x+2x-12=0….(x-6)(x+2)=0\)
So x is 6, and distance traveled by A=120/6=20
C
How you consider 60 while finding distance in algebric method(2nd option)??I can't understand