Sulekha intends to read a 200 page book within a specific period-She starts by reading 11 pages on the first day and increases her rate of reading by reading an extra 2 pages for each subsequent day How long will she take to finish reading the book?
A) 20 B) 10 C) 15 D) 25
Answers
Answer:
⇒ Sulekha will take 10 days to complete the book
⇒ option (B) is correct answer
Step-by-step explanation:
Given data
Sulekha intends to read a 200 page book
she started with 11 pages on 1st day
increases her rate of reading by reading an extra 2 pages for each subsequent day
here we need to find how long will she take to finish reading the book
Sulekha started with 11 pages and she increases 2 pages on next day
then she reading the book in following sequence
on 1st day 11 pages
on 2nd day 13 pages
on 3rd day 15 pages .. etc
the number of the pages on each day are in sequence
11, 13, 15... which are in AP
here 1st term a = 11 and common difference = 2
now find at which term the sum of the terms will be 200
we know that sum of n terms = = 200
=
= n [ 22 + 2n - 2 ] = 400
= n [ 20 + 2n] = 400
= 2n [ 10 +n] = 400
= n [ 10 + n ] = 200
= n [ 10 + n ] = 10 [ 10 + 10] [ 200= 10(20) ]
⇒ Sulekha will take 10 days to complete the book
⇒ option (B) is correct answer