Question 15

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Jambmaths question: 

The time taken to a piece of work is inversely proportional to the number of men employed. If it takes 45 men to do a piece of work in 5 days, how long will it take 25 men?

Option A: 

15 days

Option B: 

12 days

Option C: 

5days

Option D: 

9days

Jamb Maths Solution: 

$\begin{align}  & \text{Let }t\text{ be the time taken} \\ & \text{Let }m\text{ the number of men} \\ & t\propto \frac{1}{m} \\ & t=\frac{k}{m}\text{   (}k=proportionality\text{ }constant) \\ & \text{when }m=45,\text{ }t=5 \\ & 5=\frac{k}{45} \\ & k=225 \\ & \text{When we have 25 men, the number of days will be} \\ & t=\frac{k}{m}=\frac{225}{25} \\ & t=9days \\\end{align}$

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