Question

On Rohini’s birthday, her mother Gita bought play station for₹(32−+1)and two-wheeler for ₹(−53+32+2) from her savings amount (−103+92+7). Rohini calculated the balance amount in her mother’s savings account and got the balance amount as −153+152+10−. But her mother told Rohini’s calculation was wrong.
Page 2of 2(a) Do you agree to Gita? Justify your approach

Answer 1

Answer:

Let the maturity period be n months,  

P be the money deposited every month which is Rs.1000  

and r be the rate of interest per annum which is 10%.

Now, the interest I received at the end of maturity is calculated by the following formula:

I=P×  

24

n(n+1)

​

×  

100

r

​

 

We are given I=5500, so  

substituting the values, we get

⇒5550=1000×  

24

n(n+1)

​

×  

100

10

​

 

⇒n(n+1)=  

100

5550×24

​

=1332

⇒n  

2

+n−1332=0

⇒n  

2

+37n−36n−1332=0

⇒(n−36)(n+37)=0

⇒n=36, −37

Since the maturity period cannot be negative, n=36.

Therefore, the total time for which the account was held was 36 months which is the same as 3 years. So the maturity period was 3 years.