River C is 300 miles longer than River D. If the sum of their lengths is 5530 miles, what is the length of each river?

Question

I need help, I can't figure out this simple equation, please help me!!

Answer 1

Hello, Alexis,

There are several ways of working this problem.  Here are some steps:

1.  Two rivers exist in this problem, River C and River D.  Set up "Let" statements:  Let C= River C  and D=River D

 

2.  Highlight key words or numbers in the problem.    "Sum" means add.

          C= 300 mi +D                                                          c   +    d    =  5,530 mi        

River C is 300 miles longer than River D. If the sum of their lengths is 5530 miles, what is the length of each river?

 

3.  Write question, such as:  Q: What is the length of each river?   Solve for c=?   and d=?

 

4.  Now, write down what you know:     c= 300 mi. + d

                                                         c+ d = 5,530 mi    

  

Solve for "d" first by substituting the value for "c" into the 2nd equation:   c+d= 5,530

                                                                                               (300 mi. + d) + d =5,530 mi

 

Note:  d=1d    Add the like terms together:  300 mi + 2d= 5,530  

 

Now, solve for "d"; subtract 300 from both sides to isolate "2d" by itself.  Then divide both sides of the equation by 2, which is the number next to "d."

After you find the value of "d," you can use substitution and  the top equation (c+d=5,530)  to find "c."

 

I will let you finish your problem.  Susan C.

                                                                                              

Answer 2

C = D + 300

 

Total length:  D + (D+300) = 5530

 

2D = 5230

 

D = 2615