w varies jointly as x and y and inversely as z. one set of values is w=112 x=4, y=8 and z= 0.2. Find w when x=8, y=10 and z=4
For all proportion problems, start with this:
Varying "directly" or product of "jointlys" or 1 if none
quantity = k · ----------------------------------------------------------
inversely variable or product of "inverselys" or 1 if none
In this problem the varying quantity is w.
the "jointlys" are x and y. We have one inversely,z. So we have x·y
on top and z on the bottom:
w = k·
>>...one set of values is w=112 x=4, y=8 and z= 0.2...<<
Substitute these values:
112 = k·
112 = k·
112 = k·
Divide both sides by 112
= k
Now substitute for k in the first equation:
w = k·
w = ·
w =
>>...Find w when x=8, y=10 and z=4...<<
Substitute those values
w =
w =
w = 14
Edwin