Question

17.
A ladder has rungs 25 cm apart. The rungs decrease uniformly in length from 45 cm at the bottom to 25 at the top. The top and the bottom rungs are 2 m apart.
 
 
 
 
(a)
The top and bottom rungs are apart at a distance :
(i)200cm             (ii)250cm             (iii)300cm               (iv)150cm 
1
(b)
Total  number of the rungs is :
(i)20                      (ii)25                       (iii)11                      
(iv)15
1
(c)
The given problem is based on  AP,  find its first term.
(i)25                     (ii)45                  (iii)11                 
(iv)13 
(d)
What is the last term of AP ?
(i)25                   (ii)45                        (iii)11                      
(iv)15
(e)
What is the length of the wood required  for the rungs  ?
(i)385cm             (ii)538cm             (iii)532cm             
(iv) 382cm

​

Answer 1

Answer:

It is given that the rungs are 25 cm apart and the top and bottom rungs are 2

2

1

m apart.

∴ the total number of rungs.

25

2

2

1

×100

+1

=

25

250

+1=11

Now, as the lengths of the rungs decrease uniformly, they will be in an A.P.

The length of the wood required for the rungs equals the sum of all the terms of this A.P.

First term, a=45

Last term, l=25

n=11

S

n

=

2

n

(a+l)

S

10

=

2

11

(45+25)=

2

11

×70=385 cm

Therefore, the length of wood is 385cm

Step-by-step explanation:

report

Answer 2

Answer:

a) 250 cm

b) 11

c) 25

d)45

e) 385 cm