How many litres of pure acid are there in 8 litres of a 20% solution

Answer: Option C

Explanation:

While calculation in terms of percentage we need to multiply by 100, so
2.09 * 100 = 209.

Answer: Option D

Explanation:

Let the origianl salary = Rs. 100

It will be 150% of (50% of 100)
= (150/100) * (50/100) * 100 = 75

So New salary is 75, It means his loss is 25%

Answer: Option B

Explanation:

Students who play cricket, n(A) = 325
Students who play football, n(B) = 175
Total students who play either or both games,
\begin{aligned}
= n(A\cup B) = 450-50 = 400\\
\text{Required Number}, n(A \cap B) \\
= n(A)+n(B)-n(A\cup B) \\
= 325 + 175 - 400 = 100
\end{aligned}

Answer: Option C

Explanation:

Let the third number is x.
then first number = (100-30)% of x
= 70% of x = 7x/10

Second number is (63x/100)

Difference = 7x/10 - 63x/100 = 7x/10

So required percentage is, difference is what percent of first number

=> (7x/100 * 10/7x * 100 )% = 10%

Answer: Option A

Explanation:

Let the original price per egg be Rs x
Then increased price will be,
\begin{aligned}
\left(\frac{130}{100}x\right) \\
=> \frac{7.80}{x}-\frac{7.80}{\frac{130}{100}x} = 3\\
=> \frac{7.80}{x}-\frac{780}{130x} = 3 \\
=> 390x = 234 \\
=> x = 0.6 \\

\text{Actual price was Rs 0.6} \\
\text{Present price per dozen will be} \\
Rs.\left(12*\frac{130}{100}*0.6 \right) \\
= Rs. 9.36
\end{aligned}