Question

a ladder has rungs 25 cm apart .the rungs decreases uniformly in length from 45 cm to 25 cm at the top .if the top and bottom rungs are 2.5 metre apart ,what is the length of the wood required for the rungs???

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Answer 1

It is given that the top and bottom rungs are 250cm apart and the gap b/w two consecutive rungs is 25cm
so no. of rungs= (250/25+1) =11.
The largest rung is 45cm long and the smallest rung is 25cm long.
Rungs are decreasing uniformly in length from 45 cm to 25 cm so the it forms an AP such that a=45cm& l=25 cn so length of wood required to form11 rungs
=n/2(a+l)cm = 11/2(45+25)cm = (11/2*70)cm =385cm = 3.85m