Write a Python program to calculate the amount payable if money has been lent on simple interest. Principal or

Exercises · Q11

Q. Write a Python program to calculate the amount payable if money has been lent on simple interest. Principal or money lent = P, Rate of interest = R% per annum and Time = T years. Then Simple Interest (SI) = (P x R x T)/ 100. Amount payable = Principal + SI. P, R and T are given as input to the program.

Uttarakhand UbseTextbookSubjective· 3mImportance★★★★★est

78% · 38/49 Questions

🔒 Locked · start free trial →

You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.

Start your 14-day free trial to unlock the full solution →

Concept understanding — Simple Interest Calculation

Simple Interest: The Cost of Borrowing (or the Reward for Saving)

Imagine you lend a friend ₹100. A year later, they return the ₹100. You're even — but you also missed the chance to use that ₹100 yourself for a whole year. That inconvenience has a price. In finance, that price is called interest.

Simple interest is the most straightforward way to calculate that price. It says: the interest you earn (or pay) each year is a fixed percentage of the original amount you started with — no matter how many years pass.

The Core Intuition

Think of it like renting money. If you rent a car for a day, you pay a fixed daily rate. If you rent it for 5 days, you pay 5 times that daily rate. Simple interest works the same way:

The Principal (P) is the amount you lend or borrow — the "car."
The Rate (R) is the daily rental charge, expressed as a percentage of the car's value — the "rent per day."
The Time (T) is how many days you keep the car — the number of years.

The total rent (interest) is just: daily rent × number of days.

The Precise Statement

\text{Simple Interest (SI)} = \frac{P \times R \times T}{100}

Where:

P = Principal (the original sum of money)
R = Rate of interest per year (in percent)
T = Time period (in years)

The Total Amount (A) you get back (or owe) at the end is:

A = P + \text{SI}

Why Divide by 100?

The rate $R$ is given as a percentage — say 10%. "10% per year" means you get ₹10 for every ₹100 you lend, each year. So for a principal $P$ , the interest for one year is:

\frac{10}{100} \times P = 0.10 \times P

That's the same as $\frac{P \times R}{100}$ . For $T$ years, you multiply by $T$ , giving $\frac{P \times R \times T}{100}$ .

A Worked Example

You deposit ₹2000 in a bank that offers 8% simple interest per year. You leave it for 3 years.

P = ₹2000
R = 8
T = 3

\text{SI} = \frac{2000 \times 8 \times 3}{100} = \frac{48000}{100} = ₹480

So after 3 years, you earn ₹480 in interest. Your total amount becomes:

A = 2000 + 480 = ₹2480

Tip

Notice that each year you earn exactly the same interest: $\frac{2000 \times 8}{100} = ₹160$ . Year 1: ₹160, Year 2: another ₹160, Year 3: another ₹160. The interest never grows because it's always calculated on the original ₹2000, not on the growing balance.

The Key Property (and its Limitation)

Simple interest is linear — the interest grows at a constant rate each year. This makes it easy to calculate and understand. …

Start your 14-day free trial to unlock the full solution →

Read P, R and T, compute SI = (P × R × T)/100, then the amount payable = P + SI:

P = float(input("Enter principal (money lent): "))
R = float(input("Enter rate of interest (% per annum): "))
T = float(input("Enter time in years: "))
SI = (P * R * T) / 100
amount = P + SI
print("Simple Interest =", SI)
print("Amount payable =", amount)

Sample run (P = 5000, R = 7.5, T = 2):

Start your 14-day free trial to unlock the full solution →

Read P, R, T as numbers, compute SI = (P × R × T)/100 and print amount = P + SI — for a sample input of P = 5000, R = 7.5, T = 2 the amount payable is 5750.0.

Another formula-to-program exercise. The pattern to internalise: take inputs → convert them to numeric types → translate the formula with correct precedence → print labelled results.

# Amount payable on simple interest
P = float(input("Enter principal (money lent): "))
R = float(input("Enter rate of interest (% per annum): "))
T = float(input("Enter time in years: "))

SI = (P * R * T) / 100        # Simple Interest
amount = P + SI               # Amount payable

print("Simple Interest =", SI)
print("Amount payable =", amount)

Key lines:

All three inputs go through float() — rate and time are frequently fractional (7.5%, 2.5 years), and input() alone would give strings, making P * R * T a TypeError.
(P * R * T) / 100 — the parentheses mirror the given formula; multiplication happens before the division by 100 either way, but writing it this way documents the intent.

Sample run (framed as an example — any inputs work):

Enter principal (money lent): 5000 …

Start your 14-day free trial to unlock the full solution →

←Previous questionQ10 — Write a Python program to convert temperature in degree Celsius to deg…→Next questionQ12 — Write a program to calculate in how many days a work will be completed…

🎓Unlock everything free for 14 days

Unlock everything free for 14 days