Question:
Michael had to pay $3795 in order to furnish the loan taken 3 years before. If the rate of simple interest was 5% then find the sum borrowed.
Correct Answer
$3300
Solution And Explanation
Solution
Given,
Amount (A) = $3795
Rate of Simple Interest (R) = 5%
Time (T) = 3 years
Thus, Principal (P) = ?
Method (1) Using Formula
Calculation of the Principal using forumula when Amount, Time and Rate of Simple Interest are given
Formula to find the Principal (P)
Amount (A) = Principal (P) + Principal (P) × Rate (R) × Time (T)
⇒ Amount (A) = Principal (P) [1 + Rate (R) × Time (T)]
⇒ A = P (1 + RT)
Using the formula to find the Amount (A), the fourth can be calculated if any three of A, P, R, and T are given
In the given question, we need to find the Principal (P)
Therefore, by substituting, Amount, Rate, and Time, in the formula A = P (1 + RT) we get
$3795 = P (1 + 5% × 3)
⇒ $3795 = P (1 + 5/100 × 3)
⇒ $3795 = P (1 + 5 × 3/100)
⇒ $3795 = P (1 + 15/100)
⇒ $3795 = P (100 + 15/100)
⇒ $3795 = P × 115/100
⇒ P × 115/100 = $3795
⇒ P = 3795/115/100
⇒ P = 3795 × 100/115
⇒ P = 3795 × 100/115
⇒ P = 379500/115
⇒ P = $3300
Thus, the sum borrowed (P) = $3300 Answer
Method (1) Using Unitary Method
Calculation of the Principal using unitary method when Amount, Time and Rate of Simple Interest are given
Calculation of the Simple Interest
Let, the principal = 100
Here, since rate of simple interest = 5% per annum
Thus, Interest = 5% of principal
⇒ Interest = 5% of 100 = 5
Thus, Simple Interest for 1 year = 5
Calculation of the Amount
Since, in the question, time = 3 years
So, we need to calculate the simple interest for the given time period, which is 3 years
Thus, Simple Interest for 3 years = 3 × Simple Interest for 1 year
= 3 × 5 = 15
Thus, simple interest for 3 years = 15
Thus, Amount (A) = Principal + Interest
⇒ Amount = 100 + 15 = 115
Calculation of the Principal
Now,
∵ If the Amount is 115, then the Principal = 100
∴ If the Amount is 1, then the Principal = 100/115
∴ If the Amount is 3795, then the Principal = 100/115 × 3795
= 100 × 3795/115
= 379500/115
= 3300
Thus, Principal = $3300
Thus, the sum borrowed = $3300 Answer
Similar Questions
(1) Jessica took a loan of $5500 at the rate of 6% simple interest per annum. If he paid an amount of $8800 to clear the loan, then find the time period of the loan.
(2) Calculate the amount due after 10 years if William borrowed a sum of $5500 at a rate of 9% simple interest.
(3) Find the amount to be paid if Susan borrowed a sum of $5650 at 4% simple interest for 7 years.
(4) Calculate the amount due if Karen borrowed a sum of $3950 at 3% simple interest for 4 years.
(5) What amount does Mary have to pay after 6 years if he takes a loan of $3050 at 7% simple interest?
(6) Calculate the amount due if William borrowed a sum of $3500 at 9% simple interest for 3 years.
(7) Calculate the amount due after 10 years if Jennifer borrowed a sum of $5250 at a rate of 6% simple interest.
(8) Calculate the amount due if Charles borrowed a sum of $3900 at 10% simple interest for 3 years.
(9) Calculate the amount due if Joseph borrowed a sum of $3700 at 9% simple interest for 3 years.
(10) Kimberly had to pay $4929 in order to furnish the loan taken 3 years before. If the rate of simple interest was 2% then find the sum borrowed.