Given that in a trianlgle the sides AB, BC, CA are in the ratio 3:4:6.
Let AB = 3k, BC = 4k and CA = 6k.
Then perimeter =3k+4k+6k = 13k
M, N, K are mid points of the sides.
By mid point theorem MN = 3k/2, NK = 4k/2 and KM = 6k/2
Hence perimeter of MNK = 13k/2 =5.2 (given)
Solve for k
k=2(5.2)/13 = 0.8
Hence sides are
AB = 3k = 3(0.8) = 2.4 in
BC = 4k= 3.2 in
CA = 4.8 in