Question

If Meena gives an interest of Rs 45 for one year at \[9\% \] rate p.a. What is the sum she has borrowed?

Answer 1

Hint: This is a basic question of simple interest. This question has many different forms, with this being one of the most basic ones. Here, we have been given the interest (represented by I), the time for what the amount was borrowed (represented by T), the annual rate of interest (represented by R) and we have to calculate the amount she had borrowed, or in other words, we have to calculate the principal (represented by P). We just need to put in the given values (the interest, the time for what the amount was borrowed, the annual rate of interest) and find the unknown value (the principal).
Formula Used:
We are going to use the formula of simple interest, which is:
 \[{\rm{Interest}} = \dfrac{{{\rm{Principal}} \times {\rm{Rate}} \times {\rm{Time}}}}{{100}}\]
or, in mathematical form it can be written as:
 \[{\rm{I = }}\dfrac{{{\rm{P}} \times {\rm{R}} \times {\rm{T}}}}{{100}}\]

Complete step-by-step answer:
Here, in the question we have been given
Interest, \[I = 45\]
Rate, \[R = 9\% \]
Time, \[T = 1\]
Principal, \[P = ?\] (to be found)
Putting the above values into the formula of simple interest, we have:
 \[45 = \dfrac{{P \times 9 \times 1}}{{100}}\]
Keeping P on one side and taking the constants on the other side, we get:
 \[\Rightarrow P = \dfrac{{45 \times 100}}{9} = 500\]
Hence, the sum Meena borrowed was Rs 500.
So, the correct answer is “500”.

Note: So, we saw that in solving questions like these, it is best to write down the given values with their symbols (as they help in identification of the formula) and also write down the unknown one. Then, by looking at the given values and their symbols we figure out which formula uses these symbols. Then we compare the possible formulae to the information given in the question and pick the one matching all the given constraints. Then we write down the formula and put in the known values into it, and find out by calculating the unknown one.