Question

A car uses 25 litres of fuel when travelling 355 kilometers. How far can it travel with 42 liters of fuel

Answer 1

`\boxed {\boxed {\sf 596.4 \ kilometers}}`

Explanation:

Let's create a proportion using this setup.

`\frac {liters}{kilometers} = (liters)/(kilometers)`

We know that 25 liters are used for 355 kilometers.

`\frac {25 \ liters}{355 \ kilometers} = (liters)/(kilometers)`

We don't know how many kilometers are used with 42 liters. Therefore we say x kilometers are used for 42 liters.

`\frac {25 \ liters}{355 \ kilometers} = (42 \ liters)/(x \ kilometers)`

`\frac {25 }{355 } = (42 )/(x)`

Cross multiply. Multiply the first numerator by the second denominator, then the first denominator by the second numerator.

`25*x=42*355`

`25x=14910`

Since we are solving for x, we need to isolate the variable. x is being multiplied by 25. The inverse of multiplication is division, so divide both sides by 25.

`(25x)/(25)=\frac {14910}{25}`

`x=596.4`

The car can travel 596.4 kilometers with 42 liters of fuel.