In expressing a length of 81.472 km as nearly as possible with the three significant digits, find the percentage error

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}

Answer: Option C

Explanation:

= (28/100) * 450 + (45/100) * 280
= 126 + 126 = 252

Answer: Option B

Explanation:

Clearly,
x% of 150 = 150 - x [as x is number of boys]

\begin{aligned}
=> x + \frac{x}{100} * 150 = 150 \\

=> \frac{5}{2}x = 150 \\

=> x = 60 \\
\end{aligned}

Answer: Option B

Explanation:

It will 20*1/100 = 1/5

Answer: Option B

Explanation:

Question of this type looks a bit typical, but it is too simple, as below...

It will be 8 * 20/100 = 1.6