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## Class 10 (Foundation)

### Course: Class 10 (Foundation)>Unit 4

Lesson 5: Word problems

# Linear functions word problem: fuel

Sal is given a verbal description of a real-world relationship involving a truck's fuel consumption, and is asked to draw the graph that represents this relationship.

## Want to join the conversation?

• What are Linear functions?
• A linear function is when, in its simplest form, there are no variables with exponents greater than 1. A linear function will result in a straight line on a graph that has a slope and a y-intercept. It can be defined by y = ax + b where a is the slope and b is the y-intercept. I hope this helped you.
• What will be my x intercept and y intercept if the question says that the line passes through the points (-3,7) and (5,-1)?
• Find the slope of the line using the formula m=(y2-y1)/(x2-x1). Find the equation of the line with the formula y-y1=m(x-x1).
To find the x-intercept, put 0 in place of y in the equation and solve it.
To find the y-intercept, put 0 in place of x in the equation and solve it.
So in your case, m=(-1-7)/(5+3) = -8/8 = -1
Equation: y-7 = -x-3
=> x+y-4=0
=> x=4, y=4
Hope this helped
• i am confused i dont get y
• Enrique is driving to Texas. he travels at 70 kilometers per hour for 2 hours, and 63 kilometers per hour for 5 hours. over the 7 hour time period what was Enrique's average speed?

can someone please explain to me this problem.
• you need to add 70+70+63+63+63+63+63, then divide it by 7, because you have to get the total number of km traveled, then divide it by the hours.
• I have to say this kind of linear functions just like prediction , even though something not really happen but you can calculate the result like how far can a car drive consumes all the fuel in tank.
Every value in the domain has a corresponding value in range , people just find out the relationship between them and use the algorithm and variables to describe this relationship, but sometimes data actually is not so "consecutive", instead, it's kind of discreate
• But even with your example of cars and gas, while it is continuous, in real life, you would not say how far can you drive with 8.34349683 gallons of gas, while you could calculate, but it has no practical purpose. So probably the smallest increment that would be used is tenths of a gallon which would create a discrete graph.
• So the equation for this problem would be

y=400-0.8x ?
• Yes, that would be the equation for the problem in the video.
• For the fuel and kilometer question in the example can we write the question in y-intercept form like this Y=400-0.8x
• Yes you can, if y is the liters of fuel and x is the kilometers driven. Nice math!