Acar can travel 15 km per 1 liter of gas. how many miles per gallon is this? ?

The   34 mi. / gal ; or, write as :  "34 miles per gallon" .

Explanation:

      Convert "15 km / L" (that is: "kilometers per Liter") to its value, in units of
  "mi / gal " (that is, "miles per gallon).

Note the following conversions.

1 km ("kilometer/s") = 1000 m ("meters");
1 m ("meter") = 3.2 ft ("feet" (plural)or "foot (singular)."
5280 ft. ("feet") = 1 mi. ("mile(s)") .


1 L ("Liter"), or ("liter") = 0.264172051242 gal ("gallon/s").

Let us solve by using a technique known as "dimensional analysis".

  (15 km / 1 L )                     =    _?_   mi. / gal ??  ;

(15 km / 1 L)*(1 L / 0.264172051242 gal)*(1000m/ 1km)* (3.2 ft /1 m)*
(1 mi. / 5280 ft)  =  _?_  mi. / gal ??

   On the left -hand side of the equation, the units of: "km", "L", "m", "ft" ; cancel to "one' ; and we are left with:

   → [(15 * 1000 * 3.2) / (0.264172051242 * 5280)]  mi. / gal ;

   →  =  [(48000) / (1394.82843055776)]  mi. / gal ;

= 34.4128345453970259 mi/ gal; round to 2 (two) significant figures ;

→ 34 mi. / gal ; or, write as 34 miles per gallon.

Num of plants = (original#ofplants)*(1.6)^t