Need help in series and sequences (1 Viewer)

[joto]

The rungs of a ladder decrease uniformly in length from 40 cm at the bottom rung to 30cm at the top rung. How many rungs are there if their total length is 5.25m?

 

[Aesytic]

your first term is 40cm
.'. a = 40
your last term is 30cm
.'. l = 30
the sum of the lengths of your rungs is 5.25m, or 525cm
therefore 525 = n/2*[a+l]
= n/2*[30+40]
=35n
.'.n=15
.'. 15 rungs

 

[joto]

Thank you