Answer: 27 logs
Explanation:
Given : Teresa is maintaining a camp fire. She can keep the fire burning for 4 hours with 6 logs.
From the given situation , it is clear that the number of log and time for fire burning are directly proportional.
The equation for direct variation :-
![(x_1)/(y_1)=(x_2)/(y_2)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/lk7okdvgv8lu2zceghaujy4vv53fo1eo2t.png)
Put ,
, where y is the number of logs need to keep the fire burning for 18 hours.
![(4)/(6)=(18)/(y)\\\\\Rightarrow\ y=(6*18)/(4)=27](https://img.qammunity.org/2020/formulas/mathematics/middle-school/6gksxn143uuyrvv82tb7usg9emwru2zs1f.png)
Hence,she needs 27 logs to keep the fire burning for 18 hours.