Dropping less than two inches per mile after emerging from the mountains, a river drains into the ocean. One Day's discharge at its mouth, 2.4 trillion gallons, could supply all of country A's households for four months. Based on this statement, determine how much water an average household uses each month. Assume that there are 100 million households in country A

so, one trillion is 1 and twelve zeros, thus 2.4 trillion is 2 trillions and 400 billions or 24 followed by eleven zeros, because the "4" is using up a space.

now, 1 million is 1 and six zeros, thus 100 millions is 100 and six zeros or 1 and 8 zeros.

now, is 2.4 trillions in four months, thus 2.4trillion/4 will give us how many gallons in 1 month.

to find how many households, simply let's divide it by 100 millions

[tex]\bf \cfrac{\stackrel{\textit{2.4 trillions}}{24\times 10^{11}}}{4}\implies \cfrac{24}{4}\times 10^{11}\implies 6\times 10^{11} \\\\\\ \cfrac{\stackrel{\textit{gallons per month}}{6\times 10^{11}}}{\stackrel{households}{1\times 10^8}}\implies \cfrac{6}{1}\times \cfrac{10^{11}}{10^8}\implies 6\times 10^{11}\times 10^{-8} \\\\\\ 6\times 10^{11-8}\implies 6\times 10^3\implies \stackrel{\textit{gallons per household}}{6000}[/tex]