O P Malhotra, S K Gupta and, Anubhuti Gangal Solutions for Exercise 4: Exercise

The machinery of a certain factory is valued at $₹18,400$ at the end of $1980$. If it is supposed to depreciate each year at $8\%$ of the value at the beginning of the year, calculate the value of the machine at the end of $1979$ and $1981$.

The present value of a scooter is $₹15,360$. If its value depreciates $12\frac{1}{2}\%$ every year, find its value after $3$ years. Write the answer in $₹$.
 

A new car is purchased for $₹2,50,000$. Its value depreciates at the rate of $10\%$ in the first year, $8\%$ in $2$nd year and then $6\%$ every year. Find its value after $4$ years. Write the answer in $₹$ in decimal.

The bacteria in a culture grows by $10\%$ in the first hour, decreases by $10\%$ in the second hour and again increases by $10\%$ in the third hour. If the original count of the bacteria in a sample is $10,000$, find the bacteria count at the end of $3$ hours.

The production of refrigerators in a factory rose from $40000$ to $48400$ in $2$ years. Find the rate of growth percentage per year. 
 

The value of a flat worth $₹5,00,000$ is depreciating at the rate of $10\%$$\mathrm{p}.\mathrm{a}.$  In how many years will its value be reduced to$₹3,64,500$?

Rachit bought a flat for $₹10$ lakh and a car for $₹3,20,000$ at the same time. The price of the flat appreciates uniformly at the rate of $20\%$ $\mathrm{p}.\mathrm{a}$., while the price of the car depreciates at the rate of $15\%$$\mathrm{p}.\mathrm{a}$. If Rachit sells the flat and car after $3$ years, what will be his profit or loss? Write the answer in $₹$.

$8,000$ workers were employed by a company to complete a job in $4$ years. At the end of first year, $5\%$ of the workers were retrenched. At the end of second year, $5\%$of those working at that time were retrenched. However, to complete the job in time, the number of workers was increased by $10\%$ of those working at the end of third year. How many workers were working during the fourth year?