New Batches at TathaGat Delhi & Noida!               Directions to CP centre
Algebra Problem
by tgnoida1240 tg - Friday, 3 October 2014, 06:00 PM
  A series S1 of five positive integers is such that the third term is half the first term and the fifth term is 20 more than the first term. In series S2, the nth term defined as the difference between the (n+1)term and the nth term of the series S1,is an arithmetic progression with a common difference of 30.

Ques.1 First term of S1 is
a) 80 b) 90 c) 100 d) 120

Ques.2 Last term of S2 is
a)50 b)60 c)70 d)NOT

Ques.3 What is the difference between second and fifth terms of S1?
a)10 b)20 c)30 d)60

Ques.4 What is the average of the terms of series S1?
a)60 b)70 c)80 d) Average is not an integer

Ques.5 What is the sum of series S2?
a)10 b)20 c)30 d)40

Re: Algebra Problem
by TG Team - Sunday, 5 October 2014, 05:17 PM
  Hi

S1: 2a, b, a, c, 2a + 20

S2: b - 2a, a - b, c - a, 2a + 20 - c

b - 2a + 30 = a - b i.e. 3a - 2b = 30
a - b + 30 = c - a
c - a + 30 = 2a + 20 - c i.e. 3a - 2c = 10

Solving them, we get a = 50, b = 60, c = 70

So series S1: 100, 60, 50, 70, 120
and series S2: -40, -10, 20, 50, 80

Now you can easily answer all the questions easily. smile

Kamal Lohia