If a,b,c are in A.P., then 3a,3b,3c are in G.P..
True
Consider the AP a,b,c.
Let b=a+d and c=a+2d.
i.e., a,a+d,a+2d are in AP.
⇒ The sequence 3a,3b,3c becomes
3a,3a+d,3a+2d.≡3a,3a×3d,3a×(3d)2, a G.P. with common ratio 3d and first term 3a.