what is the rule/equation for this problem?

Question

two brothers, martin and morris are in their backyard. morris is taking down a wall on one side while martin is building a wall on the other side. martin starts from scratch and lays 2 bricks every minute. meanwhile, morrir takes down 3 bricks each minute from the wall. it takes morris 55 minutes to finish tearing down his wall.



i've figured out the rule for martin and its y=0+2x (y being the amount of bricks and x being the minutes) but i can't figure out the rule for morris! help please?

Answer 1

The missing piece of information is, "How many bricks are in Morris' wall when he starts?"

If he takes down 3 bricks per minute, and it takes him 55 minutes to tear down the wall, then there must have been:

3 bricks/min * 55 min = 165 bricks

when Morris started.

So the equation for Morris is y = 165 - 3x.

Answer 2

The missing piece of information is, "How many bricks are in Morris' wall when he starts?"

If he takes down 3 bricks per minute, and it takes him 55 minutes to tear down the wall, then there must have been:

3 bricks/min * 55 min = 165 bricks

when Morris started.

So the equation for Morris is y = 165 - 3x.

Answer 3

If Martin's is y = number of bricks installed = 0 + 2x, then Morris's equation can be written in two ways.

1) find the equation of how many bricks morris has removed as a functgion of x.
y=3x

2) find the equation for how many bricks are remaining in Morris's wall as a function of x.

first, how many bricks did he remove = 55 minutes * 3 bricks per minute = 165

so the equation would be y=165-3x

Answer 4

z - 3*55 = 0
or
z - 165 =0

where z is the number of bricks removed by morrir.

Answer 5

b = r * t

b = bricks in the wall
t = time to take down the wall (55 min)
r = rate (3 bricks/min)

So, b = 3*55.