Answer:
k = 0.5
Step-by-step explanation:
Given a varies directly with x² then the equation relating them is
a = kx² ( k is the constant of variation )
To find k use the condition a = 8 when x = 4 , then
8 = k × 4² = 16k ( divide both sides by 16 )
0.5 = k
0, -2 i think :p
Because i say so
B.25.12
Solution
C=2πr=2·π·4≈25.13274cm
Hope this helps!