SOLUTION: <pre>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.

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Question 50474: 
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?
Found 2 solutions by tutorcecilia, AnlytcPhil:
Answer by tutorcecilia(2152) About Me  (Show Source):
You can put this solution on YOUR website!
Bike = Scooter + $100
Scooter = Skateboard + $60
Skateboard = unknown cost = x
Total cost of all three = $310
.
Bike + Scooter + Skateboard = $310 [Basic addition formula]
.
(Scooter + 100) + (Skateboard + 60) + (Skateboard) = 310 [Plug-in the values]
.
[(Skateboard + 60) + 100) + (Skateboard + 60) + (Skateboard)] = 310
[Substitute the value of the scooter for "skateboard + 60"]
.
((x + 60) + 100) + (x + 60) + (x) = 310 [Substitute "x" for "skateboard"]
.
x + 60 + 100 + x + 60 + x = 310 [Remove the parentheis and simplify (add)]
3x + 220 = 310 [Here is the simplified equation of the problem]
3x + 220 - 220 = 310 - 220 [solve for x]
3x= 90
3x/3=90/3
x=30
.
Plug-in the values of the scooter to find the value of the other items:
Bike = Scooter + $100
Scooter = $30 + $60 = $90
Skateboard = x = $30
Total cost of all three = $310
.
Bike = $90 + $100 = $190
Scooter = $30 + $60 = $90
Skateboard = x = $30
Total cost of all three = $310
.
Check by plugging in all of the values back into the basic formula of addition
190+90+30=310
310=310 [Checks out]





Answer by AnlytcPhil(1808) About Me  (Show Source):
You can put this solution on YOUR website!
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  n + n+60 + n+60 + 100 = 310 

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