IM SO CONFUSED!!!

Question

the diameter of a U.S penny is 3/4 inch. How many pennies would it take to make a row 42 inches long?

Answer 1

Hi, Elise,

Try something like this:  Step 1:   Set up the ratios.

 

Here are the ratios:    1 penny = 3/4 in.           

                         _______ pennies = 42 in    Let "x" stand for the number of pennies in 42 inches.

 

 

Step 2:  Set up the proportion:      1 penny =   x         

                                                   3/4 in.        42 in.

 

One penny is to 3/4 inch as how many pennies is to 42 inches?

 

 

Step 3:  Cross multiply:      1* 42 = (3/4)X               42= (3/4)X

 

 

Step 4:  To get rid of fraction on the right side multiply both sides of the equation by  the reciprocal of 3/4, which is 4/3.

                        4 (42)= 4  (3)   x             Note:  4/3 *(3/4)=1              1*x=x

                        3           3  (4)

 

 

Step 5:  Simplify, and you are done:      (4)*42 =x           Multiply 4*42  for the numerator and 3*1 for denominator.

                                                            3    1

 

Note: I added a "1" under the "42" as a denominator.  Doing this did not change the value of "42".  However, it did make it easier to multiply.

 

I hope that this method is helpful.  Susan C.

Answer 2

Divide the length of the row by the diameter of one penny, and that gives you the number of pennies in the row.

 

(42 inches) / (3/4 inch) = ? 

 

Can you finish from here?