# A ladder has rungs 25cm apart. The rungs decrease uniformly in length from 45cm at the bottom to 25cm at the top. If the top and the bottom rungs are 2 1/2 m apart, what is the length of the wood required for the rungs? hint.. Number of rungs=250/25+1 Hint

Answer :   Distance between the starting rung and the top most rung =250cm

⇒  Number  of rungs in 250 cm with spacing of 25 cm = ( 250 /25) =10

⇒   Including the bottom most rung the total number of rungs on the ladder =11

⇒  The lenght of rungs is an Arithmetic Progression

⇒  Sum of lengths of all 11 rungs =[ ( 1st term + last term) /2 ] × number of rungs = [( 45 + 25 )/2]× 11 =385 cm

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