5/7(7/5z) what is value of z

Question

I am doing my homework and stuck on this I came up with z equals 1 or  you cross multiply 

Answer 1

5/7(7/5z)  This EXPRESSION is easily simplified, as far as the COEFFICIENT is concerned; as Jacoby points out, the (5/7) times (7/5) comes out as ONE.

 

But it is not clear where the z (variable) belongs.  If the denominator inside the original  parenthesized part is 5z, then the final simplification of this expression is 1/z, otherwise the final answer is z.

 

THIS CONFUSION COMES ABOUT BECAUSE OF THE UNCERTAINTY of the denominator being translated from normal math notation which uses an horizontal bar over a denominator such as 5z.  As you present it, changing the division to the simple / character, his introduces a doubt as to whether you intended 7/(5z).

Answer 2

Alan, 

 

You don't cross multiply when multiplying fraction, rather, you can cross reduce. Many students get this confused with cross multiplying ratios that are equal to each other. 

 

With that being said, we can cross reduce and 5/7 * 7/5 and come up with one. 

 

Hope this helps!

 

Jacoby