600 students took the test on physics and chemistry. 35% students failed in physics and 45% students failed in chemistry and 40% of those who passed in chemistry also passed in physics, then how many students failed in both:

Correct Answer: 140

Explanation:

x - 35 = 80x/100 

=> x = 175 

=> 4x/5 = 4x175/5 = 140.

Correct Answer: Rs.2,24,000

Explanation:

One-quarter of one-seventh = 1/4 x 1/7
= 1/28
Now, 1/28 of a land costs = Rs. 30,000
Thus, 8/35 of the land will cost = 30,000 x 28 x 4/15
= Rs. 2,24,000.

Correct Answer: 20

Explanation:

Let the rquired number be 'P'

According to the question,

$$\begin{gathered} 100 x P 100 = 20 \\ = > P = 20 x 100 100 = 20 \end{gathered}$$

Hence, 100 percent of the number 20 is 20.

 

Now, you can also try for

20 percent of what number is 100

$$\begin{gathered} 20 x P 100 = 100 \\ = > P = 100 x 100 20 = 500 \\ = > P = 500 \end{gathered}$$

Hence, 20 percent of the number 500 is 100.

Correct Answer: 100 & 4

Explanation:

Let the first number be x and the second number be y.

Given

5% of x = (25% of y) + y

=> 5x/100 = 5y/4

=> x = 25y ......(1)

and also given that, x - y = 96

=> x = 96 + y .....(2)

From (1)&(2)

25y = 96 + y

=> 24y = 96

=> y = 4

From (1)

x = 96 + 4 = 100

Hence, the numbers are 100 & 4.

Correct Answer: 1% decrease

Explanation:

Net % effect on revenue = - 10 + 10 -(10×10)/100 = - 1 Hence % reduction in revenue = 1%

Correct Answer: 12.5% more

Explanation:

    Quantity  X  Rate =  Price

 

         1  x  1  =  1

 

       0.7 x 1.25 = 0.875

 

      Decrease in price = (1-0.875) x 100 = 12.5%

Correct Answer: -99%

Explanation:

By mistake = x/10 

 

Actual value = x * 10 

 

% Change =  10 x - x 10 10 x × 100 = 99 100 × 100  = 99% (negative)

 

Since actual value is greater than the wrong value.

Correct Answer: 33.33%

Explanation:

% Decrease in Width =  50 150 x 100

 

= 33.33% 

Correct Answer: 400

Explanation:

1st day the girl read = 40%

2nd day she read = 34 %

Remaining percentage of book = 100% - (40% +34%) = 26%

But given last two days she read equal number of pages

=> Each day she read 26%/2 = 13%

Last day she read 52 pages = 13%

13% = 52

1% = 4

=> 100% = 400

Total pages in the book is 400.

Correct Answer: 180

Explanation:

Given total number of cows = k
Now, 1st son share = k/2
2nd son share = k/4
3rd son share = k/5
4th son share = 9

(k) + (k/4) + (k/5) + 9 = k
=> k - (19k/20) = 9
=> (20k-19k)/20 = 9
=> k = 180.