In a mixture of 60 L, the ratio of milk and water is 2 : 1. If the ratio of milk and water is to be 1 : 2, then the amount of water to be further added must be?

Students in the first class / Students in second class = (40 - 30)/(30 - 25) = 10/5 = 2/1
? Students in first class = 2 x 30 = 60

Profit of A/Profit of B = (Amount x Number of months) / (Amount x Number of months)
= (10000 x 12)/(5000 x 8) = 3/1
? Profit share of A = [3/(3 + 1)] x 2000 = ? 1500

A : B = 1¹/₂ = 3 : 2 = 3 x 7 : 2 x 7 = 21 : 14
B : C = 1³/₄ : 1 = 7 : 4 = 7 x 2 : 4 x 2 = 14 : 8
? A : B : C = 21 : 14 : 8
? C's share = [8/(21 + 14 + 8)] x 1290 = ? 240

They start with total of (50 x 3) = ? 150 and they return after the trip with (20 + 30 + 40) = ? 90.
So, to settle their accounts, each person must have 90/3 = ? 30 with them,
Hence, C must pay ? 10 to A

Let the expenditure and saving be ? 26y and ? 3y, respectively.
Then, according to the question,
26y + 3y = 7250
? 29y = 7250
? y = 7250/29
? y = 250
So, his monthly saving is (250 x 3) i., e ? 750

Let the number of boys and girls are 7k and 5k, respectively.
Given, total number of students = 2400
? 7k + 5k = 2400
? 12k = 2400
? k = 200
? Required number of girls = 5k = 5 x 200 = 1000

Let a + b = 6k, b + c = 7k, c + a = 8k ...(i)
and a + b + c = 14 ...(ii)

From Eq. (i),
a + b + b + c + c + a = 6K + 7K + 8K
? 2(a + b + c) = 21K
? 2 x 14 = 21K
? K = 28/21 = 4/3

? a + b 6k = = 6 x 4/32 = 8
Subtracting Eq. (iii) from Eq. (ii), we get
(a + b + c) - (a + b) = 14 - 8 = 6

Let 1st number = x and 2nd number = y
According to the question 1/2 of x = 65% of y
? x/y = 130/100 = 13/10
? x : y = 13 : 10

Let the number be 3k and 4k.
According to the question,
(3k + 3)/(4k+ 3) = 4/5
? 5(3k + 3 ) = 4(4k + 3)
? 15k + 15 = 16k + 12
? k = 15 - 12 = 3
? Difference between the numbers = (4k - 3k) = k = 3

Let the smaller number = M and the greater number = N
According to the question ,
(N - M/2) = 4(M - M/2)
? N - M/2 = 4M/2
? N = 2M + M/2
? N = 5M/2
? N : M = 5 : 2