In a college, the ratio of the number of boys to girls is 8 : 5. If there are 200 girls, the total number of students in the college is

Answer: Option C

Explanation:

let x = 1k and y = 3k, so
\begin{aligned}
= \frac{7(k)+3(3k)}{2(k)+1(3k)} \\
= \frac{16k}{5k} \\
= 16:5
\end{aligned}

Answer: Option D

Explanation:

From question, lets assume that two numbers are 3x and 5x.

\begin{aligned}
\text{then, }\frac{3x - 9}{ 5x - 9} = \frac{12}{23}\\
=> \text{23(3x - 9) = 12(5x - 9)}\\
=> 9x = 99 \\
=> x = 11
\end{aligned}
So numbers are 3(11) = 33, 5(11) = 55.
Smaller number is 33.

Answer: Option A

Explanation:

Let x is subtracted.
Then,
\begin{aligned}
\frac{(6-x)}{(7-x)}< \frac{16}{21} \\

21(6—x) < 16(7—x)\\
=> 5x > 14 = x > 2.8
\end{aligned}

Least such number is 3

Answer: Option D

Explanation:

Let the first number is A and second number is B.

As per question

\begin{aligned}
\frac{40}{100}A = \frac{2}{3}B \\

\frac{A}{B} = \frac{2}{3}*\frac{100}{40} \\
\frac{A}{B} = \frac{5}{3} \\
=> A:B = 5:3

\end{aligned}

Answer: Option B

Explanation:

Let the boy are 8x and Girls are 5x

=> 5x = 200
=> x = 40

Total students = 8x+5x = 13x = 13(40) = 520