Simple Interest
Math MCQs

Question :    James had to pay $3180 in order to furnish the loan taken 3 years before. If the rate of simple interest was 2% then find the sum borrowed.

Correct Answer  $3000

Solution & Explanation

Solution

Given,

Amount (A) = $3180

Rate of Simple Interest (R) = 2%

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

$3180 = P (1 + 2% × 3)

⇒ $3180 = P (1 + ²/₁₀₀ × 3)

⇒ $3180 = P (1 + ^{2 × 3}/₁₀₀)

⇒ $3180 = P (1 + ⁶/₁₀₀)

⇒ $3180 = P (^{100 + 6}/₁₀₀)

⇒ $3180 = P × ¹⁰⁶/₁₀₀

⇒ P × ¹⁰⁶/₁₀₀ = $3180

⇒ P = ³¹⁸⁰/_¹⁰⁶/100

⇒ P = 3180 × ¹⁰⁰/₁₀₆

⇒ P = ^{3180 × 100}/₁₀₆

⇒ P = ³¹⁸⁰⁰⁰/₁₀₆

⇒ P = $3000

Thus, the sum borrowed (P) = $3000 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 = 2% per annum

Thus, Interest = 2% of principal

⇒ Interest = 2% of 100 = 2

Thus, Simple Interest for 1 year = 2

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 × 2 = 6

Thus, simple interest for 3 years = 6

Thus, Amount (A) = Principal + Interest

⇒ Amount = 100 + 6 = 106

Calculation of the Principal

Now,

∵ If the Amount is 106, then the Principal = 100

∴ If the Amount is 1, then the Principal = ¹⁰⁰/₁₀₆

∴ If the Amount is 3180, then the Principal = ¹⁰⁰/₁₀₆ × 3180

= ^{100 × 3180}/₁₀₆

= ³¹⁸⁰⁰⁰/₁₀₆

= 3000

Thus, Principal = $3000

Thus, the sum borrowed = $3000 Answer

Similar Questions

(1) Find the amount to be paid if James borrowed a sum of $5000 at 7% simple interest for 8 years.

(2) Susan had to pay $3869 in order to furnish the loan taken 3 years before. If the rate of simple interest was 2% then find the sum borrowed.

(3) What amount does Linda have to pay after 5 years if he takes a loan of $3350 at 4% simple interest?

(4) Barbara took a loan of $5100 at the rate of 10% simple interest per annum. If he paid an amount of $10200 to clear the loan, then find the time period of the loan.

(5) What amount does Susan have to pay after 6 years if he takes a loan of $3650 at 9% simple interest?

(6) What amount does Charles have to pay after 5 years if he takes a loan of $3900 at 9% simple interest?

(7) What amount will be due after 2 years if Donald borrowed a sum of $3750 at a 8% simple interest?

(8) How much loan did Barbara borrow 5 years ago at a rate of simple interest 3% per annum, if he paid $6382.5 to clear it?

(9) Find the amount to be paid if Mary borrowed a sum of $5050 at 4% simple interest for 8 years.

(10) Calculate the amount due if Charles borrowed a sum of $3900 at 4% simple interest for 3 years.