A number is doubled and 9 is added. If the resultant is trebled, it becomes 75. What is that number ?

Correct Answer: 0.5

Explanation:

In mathematics, a geometric progression, also known as a geometric sequence, is a sequence of numbers where each term after the first is found by multiplying the previous one by a fixed, non-zero number called the common ratio.

 

Herein the given sequence, 4, 2, 1, 0.5, 0.25, 0.125,...

Common Ratio r = 2/4 = 1/2 = 0.5/1 = 0.25/0.5 = 0.125/0.25 == 0.5.

Correct Answer: 4

Explanation:

Let the number be x. Then,

15x - x = 56

x = 4

Correct Answer: 3 hrs

Explanation:

Let t be the usual time. If the usual rate is 1 unit, then the unusual rate is 6/7.
Balance by the distance,
1 x t = (6/7)(t + 30)
7t = 6(t + 30)
we get t as,
t = 180 minutes = 3 hrs.

Correct Answer: 6 painters

Explanation:

Two painters can complete two rooms in two hours.So 18 rooms can be painted in 6 hrs by 6 painters

Correct Answer: 253

Explanation:

Let the middle digit be x.

Then, 2x = 10 or x = 5. So, the number is either 253 or 352

Since the number increases on reversing the digits, so the hundred's digit is smaller than the unit's digit.

Hence, required number = 253.

Correct Answer: 2/3

Explanation:

Let the fraction be x/y. Then, x /(y+1) = 1/2

=> 2x - y = 1  ..........(i)and 

(x + 1) / y = 1  => x - y =  1 .......(ii)

 Solving (i) and (ii), we get :  x  = 2, y = 3. Hence, the required fraction is 2/3..

Correct Answer: data inadequate

Explanation:

Let the ten's digit be x and unit's digit be y. Then, (10x + y) - (x + y) = 9 or x = 1.

From this data we cannot find  y, the unit's digit. So the data is inadequate..

Correct Answer: 5

Explanation:

This is a quadratic equation. To find n we multiply the last terms in each bracket together (2 times -5) = -10

To find ?a? we multiply the first terms in each bracket together (3x times 2x) = 6x2, So a = 6.

Thus a - n = 16

To find k we multiply the first term in the first bracket by the second term in the second bracket and add the result to the product of the second term in the first bracket and the first term in the second. (-15x + 4x) = -11x. So k = -11

16 - 11 = 5

Correct Answer: 15

Explanation:

Let number of hit shots be 'X'
Let number of miss shots be 'Y'
Given X + Y = 40....(1)
50X - 10Y = 500.....(2)
Solving 1 and 2, we get
X = 15 and Y = 25
Therefore, number of hits = 15

Correct Answer: 17

Explanation:

Any two digit number can be written as (10P + Q), where P is the digit in the tens place and Q is the digit in the units place.
P + Q = 8 ----- (1)
(10Q + P) - (10P + Q) = 54
9(Q - P) = 54
(Q - P) = 6 ----- (2)
Solve (1) and (2) P = 1 and Q = 7
The required number is = 17