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.

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.

x - 35 = 80x/100 

=> x = 175 

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

                  Physics             Chemistry

Failed           35%                    45%

Passed         65%                    55%

Passed in both = 22% of total student

percentage of students who are passed in any of the physics or chemistry or both =(65+55) - 22 = 98%

So, the percentage of students who are failed in both = 2%

Therefore, total failed (in both subjects) students = 12 

    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%

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.

% Decrease in Width =  50 150 x 100

= 33.33% 

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.

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.

Total Items = 7
Discounted = 1
Percentage = 1/7 x 100
= 14.285%