Math Problem Statement

You can save Rs.5,000 a year for 3 years, and Rs.7,000 a year for 7 years thereafter. What will these savings cumulate to at the end of 10 years, if the rate of interest is 8%? *

Your answer

Solution

To solve this problem, we need to calculate the future value of the savings at the end of 10 years. The savings consist of two parts: Rs.5,000 per year for the first 3 years and Rs.7,000 per year for the next 7 years. The interest rate is 8%.

Step 1: Calculate the future value of Rs.5,000 saved annually for the first 3 years

The future value of an annuity can be calculated using the formula:

FV=A×(1+r)n1rFV = A \times \frac{(1 + r)^n - 1}{r}

Where:

  • A=5,000A = 5,000 Rs.
  • r=0.08r = 0.08 (8% interest rate)
  • n=3n = 3 years

FV1=5,000×(1+0.08)310.08FV_1 = 5,000 \times \frac{(1 + 0.08)^3 - 1}{0.08}

FV1=5,000×1.25971210.08=5,000×3.246416,232.01 Rs.FV_1 = 5,000 \times \frac{1.259712 - 1}{0.08} = 5,000 \times 3.2464 \approx 16,232.01 \text{ Rs.}

Step 2: Calculate the future value of Rs.16,232.01 at the end of 10 years

Since Rs.16,232.01 is accumulated at the end of 3 years, we need to calculate its value at the end of 10 years (which is 7 more years). This is done by compounding it forward:

FV1(after10years)=16,232.01×(1+0.08)7FV_1 (after 10 years) = 16,232.01 \times (1 + 0.08)^7

FV1(after10years)=16,232.01×1.7138227,819.49 Rs.FV_1 (after 10 years) = 16,232.01 \times 1.71382 \approx 27,819.49 \text{ Rs.}

Step 3: Calculate the future value of Rs.7,000 saved annually for the next 7 years

Now, calculate the future value of the Rs.7,000 saved annually for the next 7 years:

FV2=7,000×(1+r)n1rFV_2 = 7,000 \times \frac{(1 + r)^n - 1}{r}

Where:

  • A=7,000A = 7,000 Rs.
  • r=0.08r = 0.08 (8% interest rate)
  • n=7n = 7 years

FV2=7,000×(1+0.08)710.08FV_2 = 7,000 \times \frac{(1 + 0.08)^7 - 1}{0.08}

FV2=7,000×1.7138210.08=7,000×8.9227562,459.25 Rs.FV_2 = 7,000 \times \frac{1.71382 - 1}{0.08} = 7,000 \times 8.92275 \approx 62,459.25 \text{ Rs.}

Step 4: Add the future values to get the total savings at the end of 10 years

TotalSavings=FV1(after10years)+FV2=27,819.49 Rs.+62,459.25 Rs.90,278.74 Rs.Total \, Savings = FV_1 (after 10 years) + FV_2 = 27,819.49 \text{ Rs.} + 62,459.25 \text{ Rs.} \approx 90,278.74 \text{ Rs.}

Final Answer:

The total savings at the end of 10 years will be approximately Rs.90,278.74.


Would you like further details or have any questions?

Relative Questions:

  1. What would be the future value if the interest rate was 10% instead of 8%?
  2. How does the time period of savings affect the final accumulated amount?
  3. What if you could save Rs.7,000 for all 10 years instead of Rs.5,000 for the first 3 years?
  4. How would the savings cumulate if the interest was compounded monthly instead of annually?
  5. What would happen if the savings started with Rs.7,000 for the first 7 years and Rs.5,000 for the last 3 years?

Tip:

When calculating future values of different savings or investments over time, break down the problem into parts and calculate the future value of each part separately before combining them.

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Math Problem Analysis

Mathematical Concepts

Compound Interest
Future Value of Annuity
Time Value of Money

Formulas

Future Value of Annuity formula

Theorems

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Suitable Grade Level

High School