If xx varies directly as yy and inversely as zz and when y=7y=7 and z=2z=2, x=14x=14, what is xx when y=16y=16 and z=4z=4?

2 Answers

x=16x=16

Explanation:

xx varies directly as yy and inversely as zz means xpropyxy and xprop1/zx1z i.e.

xpropy xx1/zxy×1z

In other words x=kxxy/zx=k×yz where kk is a constant

Since when y=7y=7 and z=2z=2, we have x=14x=14, we have

14=kxx7/214=k×72 and k=14xx2/7=4k=14×27=4

and hence x=4y/zx=4yz

and when y=16y=16 and z=4z=4

z=4xx16/4=16z=4×164=16

Jun 14, 2017

x=16x=16

Explanation:

"the initial statement is " xpropy/zthe initial statement is xyz

"to convert to an equation multiply by k the constant of"to convert to an equation multiply by k the constant of
"variation"variation

rArrx=kxxy/z=(ky)/zx=k×yz=kyz

"to find k use the condition given for x,y and z"to find k use the condition given for x,y and z

x=14,y=7,z=2x=14,y=7,z=2

x=(ky)/zrArrk=(xz)/y=(14xx2)/7=4x=kyzk=xzy=14×27=4

rArr"equation is " color(red)(bar(ul(|color(white)(2/2)color(black)(x=(4y)/z)color(white)(2/2)|)))

"when " y=16" and " z=4

rArrx=(4xx16)/4=16