Question 25194
The elvator went at 4m/s at a distacne of x
The elvator reutrned at 5m/s at a distance of x
Total time in SECONDS. because its meters per second. (4*2+1)/2=4.5*60=270s
270s-90s=180s


{{{x/4+x/5=180}}}
4*5 =20
5*4=20
Hence the common multiple is 20


{{{20(x/4)+20(x/5)=20(180/1)}}}
Simplfy the expression.
5x+4x=3600
9x=3600
x=400


Hence the tower is 400m tall.
Paul.