Question

If z varies directly as x , and z =30 wnhen x =8,find z when x=4

Answer 1

15

Explanation:

`using \: \: \: \: inverse \: \: variation`

• Z=kX where k is constant
• make k subject of the formula then, k=Z/X
• for k=Z1/X1=Z2/X2
• Z1=30, X1=8, Z2=?, X2=4

30/8=Z2/4

• cross multiply

Z2=(30×4)/8

Z2=120/8

Z2=15