A man bought a piece of land for Rs [tex]$80,00,000$[/tex] on the [tex]$25^{\text{th}}$[/tex] Baisakh of 2075 BS and started constructing a house on the same day. The construction of the house was completed at a cost of Rs [tex]$2,70,00,000$[/tex]. If the price of the land increases at a rate of [tex]$20\%$[/tex] per year and the price of the house decreases at a rate of [tex]$20\%$[/tex] per year, then:

(a) What does [tex]$R$[/tex] indicate in the formula for the price after [tex]$T$[/tex] years: [tex]$\left( P_{T} \right)= P \left(1+\frac{R}{100}\right)^{T}$[/tex]? [1K]

(b) What will be the price of the land after 2 years? [2U]

(c) What will be the price of the house after 2 years? [2U]

(d) Will the prices of the land and house be the same after 2 years? If not, in how many years will the prices of the land and house be equal? [2HA]

Answers:
(a) Rate of increase in price
(b) Rs [tex]$1,15,20,000$[/tex]
(c) Rs [tex]$1,72,80,000$[/tex]
(d) 3 years



Answer :

Alright, let's break down this problem step by step.

### Question (a):
What does [tex]\( R \)[/tex] indicate in the formula [tex]\( P_{T} = P \left(1 + \frac{R}{100}\right)^{T} \)[/tex]?

In this formula, [tex]\( P_T \)[/tex] denotes the price after [tex]\( T \)[/tex] years, [tex]\( P \)[/tex] is the initial price, and [tex]\( R \)[/tex] is the rate of increase or decrease in price per year. Therefore, [tex]\( R \)[/tex] represents the annual percentage rate of change (either increase or decrease) in the price.

### Question (b):
What will be the price of the land after 2 years?

Let's start with the initial price of the land:

[tex]\[ P_{\text{land\_initial}} = 80,00,000 \text{ Rs} \][/tex]

The annual rate of increase in the price of the land is:

[tex]\[ R_{\text{land}} = 20\% \][/tex]

The number of years,

[tex]\[ T = 2 \][/tex]

The formula to calculate the price after [tex]\( T \)[/tex] years is:

[tex]\[ P_{\text{land\_2\_years}} = P_{\text{land\_initial}} \times \left(1 + \frac{R_{\text{land}}}{100}\right)^{T} \][/tex]

Plugging the values into the formula:

[tex]\[ P_{\text{land\_2\_years}} = 80,00,000 \times \left(1 + \frac{20}{100}\right)^{2} \][/tex]

[tex]\[ = 80,00,000 \times (1.20)^{2} \][/tex]

[tex]\[ = 80,00,000 \times 1.44 \][/tex]

[tex]\[ = 1,15,20,000 \text{ Rs} \][/tex]

Thus, the price of the land after 2 years is:

[tex]\[ 1,15,20,000 \text{ Rs} \][/tex]

### Question (c):
What will be the price of the house after 2 years?

Let's start with the initial price of the house:

[tex]\[ P_{\text{house\_initial}} = 2,70,00,000 \text{ Rs} \][/tex]

The annual rate of decrease in the price of the house is:

[tex]\[ R_{\text{house}} = -20\% \][/tex]

The number of years,

[tex]\[ T = 2 \][/tex]

The formula to calculate the price after [tex]\( T \)[/tex] years is:

[tex]\[ P_{\text{house\_2\_years}} = P_{\text{house\_initial}} \left(1 + \frac{R_{\text{house}}}{100}\right)^{T} \][/tex]

Plugging the values into the formula:

[tex]\[ P_{\text{house\_2\_years}} = 2,70,00,000 \times \left(1 - \frac{20}{100}\right)^{2} \][/tex]

[tex]\[ = 2,70,00,000 \times (0.80)^{2} \][/tex]

[tex]\[ = 2,70,00,000 \times 0.64 \][/tex]

[tex]\[ = 1,72,80,000 \text{ Rs} \][/tex]

Thus, the price of the house after 2 years is:

[tex]\[ 1,72,80,000 \text{ Rs} \][/tex]

### Question (d):
Will the prices of the land and house be the same after 2 years? If not, in how many years will the prices of the land and house be equal?

From parts (b) and (c) above, the price of the land after 2 years is [tex]\( 1,15,20,000 \text{ Rs} \)[/tex] and the price of the house after 2 years is [tex]\( 1,72,80,000 \text{ Rs} \)[/tex]. Clearly, these are not equal. Thus, the prices of the land and house will not be the same after 2 years.

To find out when they will be equal, we use the formula for both land and house:

1. For land: [tex]\( P_{\text{land}} = P_{\text{land\_initial}} \left(1 + \frac{R_{\text{land}}}{100}\right)^T \)[/tex]
2. For house: [tex]\( P_{\text{house}} = P_{\text{house\_initial}} \left(1 + \frac{R_{\text{house}}}{100}\right)^T \)[/tex]

We set these two equations equal to each other to find [tex]\( T \)[/tex]:

[tex]\[ 80,00,000 \times (1.20)^T = 2,70,00,000 \times (0.80)^T \][/tex]

Solving for [tex]\( T \)[/tex]:

[tex]\[ (1.20)^T = \frac{2,70,00,000}{80,00,000} \times (0.80)^T \][/tex]

[tex]\[ (1.20)^T = 3.375 \times (0.80)^T \][/tex]

Taking the natural logarithm on both sides to solve for [tex]\( T \)[/tex]:

[tex]\[ T \approx 3 \][/tex]

Thus, the prices of the land and house will be equal after approximately 3 years.

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