A stationer buys diaries at 75 rupees per dozen and sells them at 15 rupees per piece. What is the profit?

Cost of 15 eggs = 75 rupees
Cost of 1 egg = 75/15 = 5 rupees,
Cost of 5 dozens, i.e. 5 x 12 = 60 x 5 = 300

Let the total number of camels be x.
Then, acording to the question,
x/4 + 2?x + 15 = x
? x - x/4 - 2 ?x = 15
? 3x - 8?x - 60 = 0
? ?x = [8 ± ?64 + 720] / 6
= (8 ± 28) / 6
? x = 36

Let the number be x and y.
Now, according to the question,
x(x + y) = 2418 .....(i)
and y(x + y) = 3666 .....(ii)
On adding Eqs. (i) and (ii), we get
x² + xy + yx + y² = 6084
? x² + 2xy + y² = 6084
? (x + y)² = 6084
? x + y = ?6084 = 78
On subtracting Eq. (ii) from Eq. (i), we get
x² + xy - yx - y² = -1248
? x² - y² = -1248
? (x + y) (x - y) = -1248
? 78(x - y) = -1248
? x - y = - 1248 / 78 = -16
? (y - x) = 16

Let the number of bangles be x. Then, x - 38 is a perfect square and x + 25 is a perfect square.
Now, using the option, we find that x = 999
999 - 38 = 961 is a perfect square.
999 + 25 = 1024 is a perfect square

7777 - N must be a perfect square.
Now, using the option, we find that N = 33
7777 - 33 = 7744 is perfect square.

From question CP/SP = 12/18 = 2/3
? Profit (%) = ( 3 - 2 ) / 2 x 100 = 50%

2nd Solution:
CP = 100/18 = 5.55 paisa
SP = 100/12 = 8.33 paisa
? Profit = (8.33-5.55)/5.55 x 100 = 50 %

Let the CP be Rs. x , then SP be 0.96x
? 0.96x = 240
? x = 250

Now the new SP = 250 X 1.1 = 275

SP = 100/12 paise
Let's CP = x
SP = 0.8x = 100/12
? x = 10/(0.8x12) paise
Therefore, CP = 100/9.6 paise

Thus the new SP (with 20% profit) = 100/9.6 X 1.2 = 100/8 paise
Hence, 8 apples can be purchased for Rs.1 to gain 20%

6% of cost price (CP) = 1425 - 1353 = 72
? CP = ( 72 x 100 ) / 6 = 1200

The cost price ( CP ) of profitable cow = 9900 / 1.1 = 9000
and profit = Rs. 900

The CP of loss yielding cow = 9900 / 0.8 =12375
and loss = Rs. 2475

So the net loss = 2475 - 900 = 1575