Meg rowed her boat upstream a distance of 32 mi and then towed back to the starting point. The total time of the trip was 18 hours. If the rate of the current was 7 mph, find the average speed of the boat relative to the water.

the average speed of the boat relative to the water is 9 mph

Step-by-step explanation:

Let x represent the speed of the boat.

The rate of the current was 7 mph,

Assuming the boat travelled against the current while going upstream, the total speed would be x - 7

Assuming the boat in the direction of the current while going downstream, the total speed would be x + 7

Time = speed × time

Since she travelled 32 miles upstream and 32 miles downstream, then,

Time taken to go upstream = 32/(x -7)

Time taken to go downstream = 32/(x + 7)

Since the total time of the trip was 18 hours, then

32/(x -7) + 32/(x + 7) = 18

Cross multiplying by (x - 7)(x + 7), it becomes

32(x + 7) + 32(x - 7) = 18[(x - 7)(x + 7)

32x + 224 + 32x - 224 = 18(x² + 7x - 7x - 49

32x + 32x = 18x² - 882

18x² - 64x - 882 = 0

Dividing through by 2, it becomes

9x² - 32x - 441 = 0

9x² + 49x - 81x - 441 = 0

x(9x + 49) - 9(9x + 49) = 0

x - 9 = 0 or 9x + 49 = 0

x = 9 or x = - 49/9

Since the speed of the boat cannot be negative, then x = 9

he used the algebra tiles correctly.

step-by-step explanation:

given : 3x(2x-1)

solution :

since he used algebra tiles .

armando's solution is the same in the solution shown in figure

as he distributed 2x into x and x and wrote them vertically

and also write   -1 vertically

and 3x into x and x and x and wrote it horizontally

performing the multiplication in the algebra tiles we get

and solving the given expression :

3x(2x-1)

since solving the expression using tiles   and solving the expression algebraically we get the same answer

thus   we can choose the first statement as the answer to this problem which is "he used the algebra tiles correctly".