SOLUTION: The number of miles per gallon of gasoline that a vehicle averages varies inversely as the average speed of the car travels. A vehicle gets 18 miles per gallon at 76 mph. How man

Algebra ->  Rational-functions -> SOLUTION: The number of miles per gallon of gasoline that a vehicle averages varies inversely as the average speed of the car travels. A vehicle gets 18 miles per gallon at 76 mph. How man      Log On


   

Question 719019: The number of miles per gallon of gasoline that a vehicle averages varies inversely as the average speed of the car travels. A vehicle gets 18 miles per gallon at 76 mph. How many miles per gallon will it get at 40 mph?
Answer by josgarithmetic(39625) About Me  (Show Source):
You can put this solution on YOUR website!
The first pieces of data give 18=k%2F78. The second piece of data gives r=k%2F40 for some unknown fuel rate of r. That altogether then is two equations and two unknowns, and as arranged, seems solvable.

Simple substitution and then simplification will do.
From 18=k%2F78, get k=18%2A78
highlight%28r=%2818%2A78%29%2F40%29=11.7 or 12 miles per gallon