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math & puzzles Online Quiz - 59

Description: math & puzzles Online Quiz - 59
Number of Questions: 20
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Tags: math & puzzles
Attempted 0/20 Correct 0 Score 0

log 2x-5logx+6=0. then what is the value of x

  1. e^2

  2. e^3

  3. e^2 or e^3

  4. none of these


Correct Option: C

AI Explanation

To solve the equation log(2x) - 5log(x) + 6 = 0 and find the value of x, we can use logarithmic properties and algebraic manipulation.

Let's go through each option to determine the correct answer:

Option A) e^2 If x = e^2, then 2x = 2e^2. Substituting these values into the equation, we get: log(2e^2) - 5log(e^2) + 6 = 0 2log(e) + 2log(2) - 5(2log(e)) + 6 = 0 2 + 2log(2) - 10 - 10log(e) + 6 = 0 -2 - 10log(e) + 6 + 2log(2) = 0 -2 - 10 + 6 + 2log(2) = 0 -6 + 2log(2) = 0 2log(2) = 6 log(2^2) = 6 4 = 6 (which is not true)

Option A is incorrect.

Option B) e^3 If x = e^3, then 2x = 2e^3. Substituting these values into the equation, we get: log(2e^3) - 5log(e^3) + 6 = 0 3log(e) + 2log(2) - 15log(e) + 6 = 0 3 + 2log(2) - 15 - 15log(e) + 6 = 0 -12 - 15log(e) + 2log(2) = 0 -12 - 15 + 2log(2) = 0 -27 + 2log(2) = 0 2log(2) = 27 log(2^2) = 27 4 = 27 (which is not true)

Option B is incorrect.

Option C) e^2 or e^3 If we substitute x = e^2, we get: log(2e^2) - 5log(e^2) + 6 = 0 2log(e) + 2log(2) - 10log(e) + 6 = 0 2 + 2log(2) - 10 - 10log(e) + 6 = 0 -8 - 10log(e) + 2log(2) = 0 -8 - 10 + 2log(2) = 0 -18 + 2log(2) = 0 2log(2) = 18 log(2^2) = 18 4 = 18 (which is not true)

If we substitute x = e^3, we get: log(2e^3) - 5log(e^3) + 6 = 0 3log(e) + 2log(2) - 15log(e) + 6 = 0 3 + 2log(2) - 15 - 15log(e) + 6 = 0 -12 - 15log(e) + 2log(2) = 0 -12 - 15 + 2log(2) = 0 -27 + 2log(2) = 0 2log(2) = 27 log(2^2) = 27 4 = 27 (which is not true)

Both x = e^2 and x = e^3 do not satisfy the equation.

Option C is incorrect.

Option D) None of these Since none of the options satisfy the equation, we can conclude that the correct answer is option D) None of these.

Therefore, the correct answer is D) None of these.

A man ate 100 bananas in 5 days,each day eating 6 more than the previous day. how many bananas did he eat on the first day?

  1. 6

  2. 8

  3. 10

  4. 12


Correct Option: B

find the least value of 3x+4y if x^2y^3=6

  1. 24

  2. 26

  3. 16

  4. 10


Correct Option: D

From a 5 different green balls,4 different blue ball and 3 different red balls,how many combinations of ball can be chosen taking atleast one green and one blue ball?

  1. 3780

  2. 3760

  3. 3740

  4. 3720


Correct Option: D

The letters A,B,C,D,E,F and G not necessarily in same order stand for seven consecutive integers from 1 to 10 D is 3 less than A B is the middle term F is as much less than B as C greater than D G is greater than F. fifth integer is:

  1. A

  2. C

  3. D

  4. F


Correct Option: A

complete the given series: 3 6 11 20 ...

  1. 34

  2. 35

  3. 36

  4. 37


Correct Option: D

average of 5 consecutive number is "n". If the next two numbers are also included,then average will be:

  1. increase by 1

  2. increase by 2

  3. increase by 1.4

  4. remain same


Correct Option: A

A cricketer whose average is 12.4 takes 5 wickets for 26 runs andb thereby decreasing his average by 0.4. The number of wickets taken by him before last match is:

  1. 82

  2. 84

  3. 85

  4. 83


Correct Option: C

After replacing an old man by a new man,average of five members team of a club is same as it was 3 years ago. What is the difference between the age of the replaced one and the new member:

  1. 4

  2. 10

  3. 8

  4. 15


Correct Option: D

Simple Interest on Rs 18200 from 09/03/2001 to 21/05/2001 at the rate 7.5 RATE PERCENT IS:

  1. 290

  2. 273

  3. 288

  4. 225


Correct Option: B

In how many years a sum of money DOUBLES itself at 4% per annum

  1. 8

  2. 16

  3. 25

  4. 20


Correct Option: C

S.I on a sum will be 6000 after 10 years.If principal triples after 5 years,what will be the total interest at the end of tenth year:

  1. 6000

  2. 9000

  3. 12000

  4. 120


Correct Option: C

a,b,c are sum of money such that b is S.I on a, c is S.I on o for same rate and same time,then:

  1. a^2=bc

  2. b^2=ac

  3. c^=ab

  4. abc=1


Correct Option: B

a,b,c are sum of money such that b is S.I on a, c is S.I on o for same rate and same time,then:

  1. a^2=bc

  2. b^2=ac

  3. c^=ab

  4. abc=1


Correct Option: B

Find simple DISCOUNT equivalent to a series of discounts 20%,10% and 25%

  1. 35

  2. 45

  3. 46

  4. 40


Correct Option: C

Find simple DISCOUNT equivalent to a series of discounts 20%,10% and 25%

  1. 35

  2. 45

  3. 46

  4. 40


Correct Option: C

If a:b=c:d Then, (pa+qc)/(pb+qd) will be

  1. p:q

  2. a:b

  3. c:d

  4. a:b and c:d


Correct Option: D

If a:b=c:d Then, (pa+qc)/(pb+qd) will be

  1. p:q

  2. a:b

  3. c:d

  4. a:b and c:d


Correct Option: D

AI Explanation

To solve this question, let's start by understanding the given equation:

a:b = c:d

This equation represents a proportion, where the ratio of a to b is equal to the ratio of c to d.

Now, let's consider the expression (pa+qc)/(pb+qd). We can simplify this expression by multiplying both the numerator and denominator by the same value.

Multiplying the numerator by p and the denominator by q, we get:

(pa+qc)/(pb+qd) = (p*a + q*c)/(p*b + q*d)

Now, let's compare this expression to the given equation a:b = c:d.

The numerator of the expression (pa+qc)/(pb+qd) is p*a + q*c, which has the same ratio as a and c.

The denominator of the expression (pa+qc)/(pb+qd) is p*b + q*d, which has the same ratio as b and d.

Therefore, the expression (pa+qc)/(pb+qd) has the same ratio as a:b and c:d.

Hence, the correct answer is option D) a:b and c:d.

Which of these nickname is Nagpur also known as

  1. City of Diamond

  2. City of Orange

  3. Pink City

  4. City of lakes


Correct Option: B

What was the name of India’s first unmanned lunar spacecraft launched in October 08

  1. Chandravahan I

  2. Chandrayaan I

  3. Chandravimaan I

  4. Chandrakhoj I


Correct Option: B
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