• Nov 18th 2007, 08:01 PM
pinkmath135
a) Two cement blocks and three bricks weigh 102lb, as do one cement block and ten bricks. What does one brick weigh?

b) A refrigerator repairman charges a fixed amount for a service call in addition to his hourly rate. If a two-hour repair costs \$50 and a four-hour repair costs \$74, what is the repairman's hourly rate?
• Nov 18th 2007, 08:10 PM
Jhevon
Quote:

Originally Posted by pinkmath135
a) Two cement blocks and three bricks weigh 102lb, as do one cement block and ten bricks. What does one brick weigh?

Let $c$ be the weight of a cement block
Let $b$ be the weight of a brick

then we have the system:

$2c + 3b = 102$ ....................(1)
$c + 10b = 102$ ....................(2)

solve this system for $b$ and you will have your answer. can you continue?

Quote:

b) A refrigerator repairman charges a fixed amount for a service call in addition to his hourly rate. If a two-hour repair costs \$50 and a four-hour repair costs \$74, what is the repairman's hourly rate?
Let $m$ be the hourly rate
Let $x$ be the number of hours the repair takes
Let $b$ be the fixed charge.

then the cost of the repair is given by:

$c = mx + b$

since a two hour repair costs \$50, we have:

$2m + b = 50$ ..................(1)

since a four-hour repair costs \$74, we have:

$4m + b = 74$ ...................(2)

thus we need to solve the following system

$2m + b = 50$ ..................(1)
$4m + b = 74$ ..................(2)

for $m$

can you continue?
• Nov 18th 2007, 08:53 PM
pinkmath135
Quote:

Originally Posted by Jhevon
Let $c$ be the weight of a cement block
Let $b$ be the weight of a brick

then we have the system:

$2c + 3b = 102$ ....................(1)
$c + 10b = 102$ ....................(2)

solve this system for $b$ and you will have your answer. can you continue?

Let $m$ be the hourly rate
Let $x$ be the number of hours the repair takes
Let $b$ be the fixed charge.

then the cost of the repair is given by:

$c = mx + b$

since a two hour repair costs \$50, we have:

$2m + b = 50$ ..................(1)

since a four-hour repair costs \$74, we have:

$4m + b = 74$ ...................(2)

thus we need to solve the following system

$2m + b = 50$ ..................(1)
$4m + b = 74$ ..................(2)

for $m$

can you continue?