A bar $1\mathrm{.}5$ m long is made up of two parts of aluminium and steel and that

cross sectional area of Aluminum bar is twice that of steel bar. The rod is

subjected to an axial tensile load of $200$ kN$.$ If the elongation in aluminium and

steel bar are equal, find the length of the two parts of the bar. Take E steel $=$

$200$GPa; E Aluminium $=$ one third of E steel.