Have given one interesting question from progressions. This is from challenge quiz I. This is not that difficult, but as with all good questions, there is a formula-based method of solving them and there is a more straightforward intuitive way of solving them. (This question can be solved without putting pen to paper. Try it)
Sum of first 25 terms in AP is 525, sum of the next 25 terms is 725, what is the common difference?
Correct Answer : 8/25. Correct Choice : (1)
The sum of the first 25 terms, S25 = 525
The sum of the next 25 terms, K25 = sum of next 25 terms = 725
a26 = a1 + 25d
a27 = a2 + 25d
K25 = a26 + a27 + …… + a50
Or K25 = a1 + 25d + a2 + 25d + …… + a25+ 25d
Or K25 = a1 + a2 + …… + a25+ 25(25d)
Or K25 = S25 + 25(25d)
i.e., 725 = 525 + 25 x 25d
200 = 25 x 25d
8 = 25d
d = 8/25
2iim – CAT Online Coaching, CAT Classes, Correspondence material.
- November 19, 2012 CAT Inequalities – Few questions
Have given three interesting questions from Inequalities.
1. Find the range of x for which (x + 2) (x + 5) > 40.
2. How many integer values of x […] Posted in Inequalities
- May 31, 2013 CAT Progressions
Second term of a GP is 1000 and the common ratio is where n is a natural number. Pn is the product of n terms of this GP. P6 > P5 and P6 > P7, what is the sum of all […] Posted in Progressions
- October 13, 2010 CAT – questions and solution from progressions
Have given one interesting question from progressions. This question is from challenge quiz I. This is not that difficult, but as with all good questions, there is a […] Posted in Progressions
- August 16, 2016 CAT Online Coaching – Question from Progressions Question
Consider a set of numbers from 1 to 751. How many Arithmetic Progressions can be formed from this set of numbers such that the first term is 1 and the last term is 751 and the […] Posted in Progressions