Question 25824
4 1/2 ----> 9/2 ---> 4.5
4.5 --> 270s
270s-90s=180s
Let the distance be x
So {{{x/4+x/5}}}=180
The common multiple is 20
{{{20(x/4)+20(x/5)=20(180/1)}}}
5x+4x=3600
9x=3600
x=400


Hence, the tower is 400m high.
Paul.