Question

$6$ typist working $5$ hours a day can type the manuscript of a book in $16$ days. How many days will $4$ typists take to do the same job, each working $6$ hrs a day?

• A. $21$ days
• B. $17$ days
• C. $18$ days
• D. $20$ days

Answer 1

Answer: (D)

$20$ days

$6$ typists working $5$ hours a day can finish the job in $16$ days
$6$ typists working $1$ hour a day can finish it in $\left(\begin{array}{c}16\times 5\end{array}\right)$ days
$1$ typist working $1$ hour a day can finish it in $\frac{16\times 5\times 6}{6}$ days
$1$ typist working $6$ hours a day can finish it in $6$ days
$4$ typists working $6$ hours a day can finish it $\frac{16\times 5\times 6}{6\times 4}$ days $=20$ days.
Hence, $4$ typists working $6$ hours a day can finish the job in $20$ days.