Insert four G.M.s between 2 and 486.

Explanation

Let four G.M.'s between 2 and 496 be `g_(1),g_(2),g_(3) and g_(4)`.
So, 2, `g_(1),g_(2),g_(3),g_(4)` 486 are in G.P..
`therefore486=2xxr^(5)`
`rArrr^(5)=243=3^(5)`
`rArrr=3`
`rArrg_(1)=2r=2xx3=6,`
`g_(2)=2r^(2)=2xx3^(2)=18`,
`g_(3)=2r^(3)=2xx3^(3)=54`,
`g_(4)=2r^(4)=2xx3^(4)=162`