Question 50474
<pre><font size = 5><b>My son is in 8th grade and I am trying to help him with 
math.  Please explain a formula to figure these types 
of problems.  Thanks

A bike costs $100 more than a scooter. A scooter costs $60 
more than a skateboard. the total cost of the 3 items is 
$310. How much is skateboard? Scooter? Bike?

Let the cost of a skateboard = n dollars

>>...A scooter costs $60 more than a skateboard...<< 

Translation:  the cost of a scooter is n+60 dollars

>>...A bike cost $100 more than a scooter...<<

Translation: the cost of a bike is (n+60) + 100

>>...the total cost of the 3 items is $310...<<

Translation: 

skateboard cost + scooter's cost + bike's cost = 310

so

equation<u>  n + n+60 + n+60 + 100 = 310 </u>

Solve for n 

             n + n+60 + n+60 + 100 = 310

Collect like terms on left:
                          3n + 220 = 310
                  
Subtract 220 from both sides                                   

                                3n = 90

Divide both sides by 3

                                 n = 30

So a skateboard costs $30

>>...A scooter costs $60 more than a skateboard...<< 

So a scooter costs $90

>>...A bike cost $100 more than a scooter...<<

So a bike costs $190

Check:

>>...the total cost of the 3 items is $310...<<

$30 + $90 + $190 = $310

So it's correct.

Edwin</pre>