17.78 gallons are required for a trip of 400 miles.
Solution:
Given, the number of gallons g of fuel used on a trip varies directly with the number of miles m traveled.
A trip of 270 miles required 12 gallons of fuel,
We have to find how many gallons are required for a trip of 400 miles?
now, according to given information,
270 miles ⇒ 12 gallons
400 miles ⇒ "g" gallons
So, by chris cross method
[tex]\mathrm{g} \times 270=400 \times 12 \rightarrow \mathrm{g}=\frac{400 \times 12}{270} \rightarrow \mathrm{g}=\frac{400 \times 4}{90} \rightarrow \mathrm{g}=\frac{40 \times 4}{9} \rightarrow \mathrm{g}=\frac{160}{9}[/tex]
= 17.77 ≈ 17.8
Hence, 17.8 gallons are required for 400 miles.
