Qus : 1
3 The sum of infinite terms of a decreasing GP is equal to the greatest value of the function
in the interval [-2,3] and the difference between the first two terms is f'(0). Then the common ratio of GP is 1 -2/3 2 4/3 3 2/3 4 -4/3 Go to Discussion
Solution Qus : 2
2 If a , b , c are in GP and l o g a − l o g 2 b , l o g 2 b − l o g 3 c and l o g 3 c − l o g a are in AP, then a , b , c are the lengths of the sides of a triangle which
is
1 Acute angle 2 Obtuse angled 3 Right Angles 4 Equilateral Go to Discussion
Qus : 4
3 If a , a , a 2 , . , a 2 n − 1 , b are in AP, a , b 1 , b 2 , . . . b 2 n − 1 , b are in GP and a , c 1 , c 2 , . . . c 2 n − 1 , b are in HP, where a, b are positive, then the
equation a n x 2 − b n + c n has its roots
1 Real and equal 2 Real and unequal 3 imaginary 4 One real and one imaginary Go to Discussion
Qus : 5
3 If x = 1 + 6 √ 2 + 6 √ 4 + 6 √ 8 + 6 √ 16 + 6 √ 32 then ( 1 + 1 x ) 24 =
1 1 2 4
3 16 4 24
Go to Discussion
Solution
Given:
x = 1 + 2 1 / 6 + 4 1 / 6 + 8 1 / 6 + 16 1 / 6 + 32 1 / 6
Step 1: Write in powers of a = 2 1 / 6
x = 1 + a + a 2 + a 3 + a 4 + a 5 = 1 + a ( a 5 − 1 ) a − 1
Step 2: Use identity a 6 = 2 ⇒ a 5 = 2 a
x = 1 + 2 − a a − 1 = 1 a − 1 ⇒ 1 + 1 x = a ⇒ ( 1 + 1 x ) 24 = a 24
Step 3: Final calculation
a = 2 1 / 6 ⇒ a 24 = ( 2 1 / 6 ) 24 = 2 4 = 16
✅ Final Answer: 16
Qus : 6
3 The number of solutions of 5 1 + | sin x | + | sin x | 2 + … = 25 for x ∈ ( − π , π ) is
1 2 2 0
3 4 4 ∞ Go to Discussion
Solution
Step 1: Recognize the series
The exponent is an infinite geometric series:
1 + | sin x | + | sin x | 2 + | sin x | 3 + ⋯
This is a geometric series with first term a = 1 , common ratio r = | sin x | ∈ [ 0 , 1 ] , so:
Sum = 1 1 − | sin x |
Step 2: Rewrite the equation
5 1 1 − | sin x | = 25 = 5 2
Equating exponents:
1 1 − | sin x | = 2 ⇒ 1 − | sin x | = 1 2 ⇒ | sin x | = 1 2
Step 3: Solve for x ∈ ( − π , π )
We want all x ∈ ( − π , π ) such that | sin x | = 1 2
So sin x = ± 1 2 . Within ( − π , π ) , the values of x satisfying this are:
✅ Final Answer: 4 solutions
Qus : 7
2 Which term of the series √ 5 3 , √ 5 4 , 1 √ 5 , . . . is √ 5 13 ?
1 12 2 11 3 10 4 9 Go to Discussion
Solution Qus : 8
3 In a Harmonic Progression, p t h term is q and
the q t h term is p . Then p q t h term is
1 0 2 pq 3 1 4 pq(p+q) Go to Discussion
Solution Qus : 9
1 If one AM (Arithmetic mean) 'a' and two GM's (Geometric means) p and q be inserted between any two positive numbers, the value of p^3+q^3 is
1 2apq 2 pq/a 3 2pq/a 4 p+q+a Go to Discussion
Solution
Problem:
If one Arithmetic Mean (AM) a and two Geometric Means p and q are inserted between any two positive numbers, find the value of:
p 3 + q 3
Given:
Let two positive numbers be A and B .
One AM: a = A + B 2
Two GMs inserted: so the four terms in G.P. are:
A , p = 3 √ A 2 B , q = 3 √ A B 2 , B
Now calculate:
p q = 3 √ A 2 B ⋅ 3 √ A B 2 = 3 √ A 3 B 3 = A B
p 3 = A 2 B , q 3 = A B 2
p 3 + q 3 = A 2 B + A B 2 = A B ( A + B )
Also,
2 a p q = 2 ⋅ A + B 2 ⋅ A B = A B ( A + B )
✅ Therefore,
p 3 + q 3 = 2 a p q
Qus : 10
3 The number of common terms in the two sequences 17, 21, 25, ..........., 817 and 16, 21, 26, ..........., 851 is
1 28 2 39 3 40 4 87 Go to Discussion
Solution Qus : 13
2 The harmonic mean of two numbers is 4. Their arithmetic mean A and the geometric mean G satisfy the relation 2A+G2 = 27, then the two numbers are
1 4 and 2 2 6 and 3 3 5 and 7 4 4 and 1 Go to Discussion
Solution Qus : 14
1 Three positive number whose sum is 21 are in arithmetic progression. If 2, 2, 14 are added to them respectively then resulting numbers are in geometric progression. Then which of the following is not among the three numbers?
1 25 2 13 3 1 4 7 Go to Discussion
Solution Let the three terms in A.P. be a – d, a, a + d.
given that a – d + a + a + d = 21
a = 7
then the three term in A.P. are 7 – d, 7, 7 + d
According to given condition 9 – d, 9, 21 + d are in G.P.
(9)2 = (9 – d) (21 + d)
81 = 189 + 9d – 21d – d2
81 = 189 – 12d – d2
d2 + 12d – 108 = 0
d(d + 18) – 6 (d + 18) = 0
(d – 6) (d + 18) = 0
We get, d = 6, –18
Putting d = 6 in the term 7 – d, 7, 7 + d we get 1, 7, 13.
Qus : 15
1 If H 1 , H 2 , … , H n are n harmonic means between a and b ( b ≠ a ) ;,then H n + a H n − a + H n + b H n − b
1 2 n 2 n + 1 3 n − 1 4 2 n + 1 Go to Discussion
Solution Qus : 16
1 If
are positive real numbers whose product is a fixed number c, then the minimum of
is
1 2 3 4 Go to Discussion
Solution Qus : 17
2 The four geometric means between 2 and 64 are
1 1 4 , 1 8 , 1 16 , 1 32 2 4 , 8 , 16 , 32 3 4 √ 2 , 8 , 16 √ 2 , 32 4 None of the above Go to Discussion
Solution Qus : 18
1 If a, b, c are in geometric progression, then l o g a a x , l o g a b x and l o g a c x are in
1 Arithmetic progression 2 Geometric progression 3 Harmonic progression 4 Arithmetico-geometric progression Go to Discussion
Solution Qus : 19
2 The value of the sum 1 2 √ 1 + 1 √ 2 + 1 3 √ 2 + 2 √ 3 + 1 4 √ 3 + 3 √ 4 + . . . + 1 25 √ 24 + 24 √ 25 is
1 9 10 2 4 5 3 14 15 4 7 15 Go to Discussion
Solution Qus : 20
1 An arithmetic progression has 3 as its first term.
Also, the sum of the first 8 terms is twice the sum of
the first 5 terms. Then what is the common
difference?
1 3/4 2 1/2 3 1/4 4 4/3 Go to Discussion
Solution Qus : 21
3 The sum of infinite terms of decreasing GP is equal to the greatest value of the function f(x) = x^3
+ 3x – 9 in the
interval [–2, 3] and difference between the first two terms is f '(0). Then the common ratio of the GP is
1 \frac{-2}{3} 2 \frac{4}{3} 3 \frac{+2}{3} 4 \frac{-4}{3} Go to Discussion
Solution
? GP and Function Relation
Given: f(x) = x^3 + 3x - 9
The sum of infinite GP = max value of f(x) on [−2, 3]
The difference between first two terms = f'(0)
Step 1: f(x) is increasing ⇒ Max at x = 3
f(3) = 27 \Rightarrow \frac{a}{1 - r} = 27
Step 2: f'(x) = 3x^2 + 3 \Rightarrow f'(0) = 3
⇒ a(1 - r) = 3
Step 3: Solve:
a = 27(1 - r)
\Rightarrow 27(1 - r)^2 = 3 \Rightarrow (1 - r)^2 = \frac{1}{9} \Rightarrow r = \frac{2}{3}
✅ Final Answer:
r = \frac{2}{3}
Qus : 22
2
If a, b, c, d are in HP and arithmetic mean of ab, bc, cd is 9 then which of the following number is the value of ad?
1 3 2 9 3 12 4 4 Go to Discussion
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