Question Detail

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

0.35%
0.34%
0.034%
0.035%

Answer: Option C

Explanation:

Error = (81.5 - 81.472) = 0.028
Required percentage = \begin{aligned}
\frac{0.028}{81.472} \times 100 = 0.034 %
\end{aligned}

1. Out of 450 students of a school, 325 play football, 175 play cricket and 50 neither play football nor cricket. How many students play both football and cricket ?

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}

2. Due to an increase in 30% in the price of eggs, 3 eggs less are available for Rs. 7.80. Find the present rate of eggs per dozen.

Rs. 9.36
Rs. 10.36
Rs. 11.36
Rs. 12.36

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}

3. 88% of 370 + 24% of 210 - x = 118

Answer: Option D

4. What will be the fraction of 20%

1/4
1/5
1/10
None of above

Answer: Option B

Explanation:

It will 20*1/100 = 1/5

5. A student multiplied a number by 3/5 instead of 5/3. What is the percentage error.

Answer: Option A

Explanation:

Let the number be x,
then,
\begin{aligned}
\frac{5}{3} - \frac{3}{5} = \frac{16}{15}x
\end{aligned}

Error% = \begin{aligned}
(\frac{16}{15}x * \frac{3}{5} * 100)% = 64%
\end{aligned}