Question

1. weight in pounds of 200 gallons of water 200 g × 8.345 lbs =
2. density of an 8 ft. 2x4 that weighs 4.5 lbs. to lbs./ft.³

Explanation:

Step1: Calculate weight of water

We know that 1 gallon of water weighs 8.345 lbs. To find the weight of 200 gallons of water, we multiply the number of gallons by the weight per gallon.
$200\times8.345 = 1669$ lbs

Step2: Calculate density of 2x4

The volume of an 8 - ft long 2x4: A 2x4 has nominal dimensions 2 inches by 4 inches. In actuality, the dimensions are 1.5 inches by 3.5 inches. First convert to feet: 1.5 inches = $\frac{1.5}{12}=0.125$ ft and 3.5 inches=$\frac{3.5}{12}\approx0.292$ ft. The volume $V$ of the 8 - ft long 2x4 is $V = 0.125\times0.292\times8=0.292$ $ft^{3}$.
The density $
ho$ is given by the formula $
ho=\frac{m}{V}$, where $m = 4.5$ lbs and $V = 0.292$ $ft^{3}$. So $
ho=\frac{4.5}{0.292}\approx15.41$ lbs/$ft^{3}$

Answer:

Weight of 200 gallons of water: 1669 lbs
Density of 8 - ft 2x4: 15.41 lbs/$ft^{3}$