Question

Mona deposited a certain sum of money in the bank account. A sum of money amounts to Rs 9000 after 5 years and 12000 after 8 years at a certain rate of simple interest, then find the sum of money that was deposited by Mona.
1. Rs 4000
2. Rs 5000
3. Rs 7200
4. Rs 8000

Answer 1

Correct Answer - Option 1 : Rs 4000

Given 

Amount after 5 years = Rs. 9000 

Amount after 8 years = Rs. 12000 

Formula Used 

Amount = Principal + Simple Interest 

Calculation 

Let the principal be P

⇒ Let the interest for 1 year be x 

⇒ So, Interest for 5 years = 5x 

⇒ and, interest for 8 years = 8x 

⇒ 12000 = P + 8x       -----(i)

⇒ 9000 = P + 5x      -----(ii)

Substract (ii) from (i)

⇒ x = 1000 

So, put the value of x in (i) 

⇒ P = 12000 – 8000 = Rs. 4000 

∴ The sum of money deposited by Mona was Rs. 4000