The sides of a triangle is 6,8,15 cm long. in a similar triangle, the longest side is 21 cm long find the two sides.

Longest Side is 15 and 21.
Find the ratio which is 21/15.
= 1.4 , so every side multiply by 1.4 will give the size of the sides of the other triangle.

*note : it's a similar triangular so enlargement is used and the enlargement factor (k) is = 1.4*

so. 6 × 1.4 = 8.4
and. 8 × 1.4 = 11.2.