Question

a sum of rs. 1000 is invested at 8% simple interest per year.Calculate the interest at the end of each year.Do these interest an A.P.? If so ,find the interest at the end of 30 years making use of this fact

Answer 1

investment is equals 1000 rupees
simple interest = 8%
interest at the end of each year
=(si x investment)/100
8x1000/100
80rs
yes it forms an ap with common difference = 80
AP is as
80, 160, 240........................upto 30terms
interest at the end of 30 years
=n/2(2xa+(n-1) xd)
n = number of terms in AP
a = first term
d = common difference of the AP
=30/2(2x80+(30-1)x80)
=15(160+2320)
=15x2480
=37200rs

Answer 2

↦Solution : -

Formula to Calculate Simple Interest is :

S.I = P × R × T/100

Now ,

The Intereset at the end of 1st year = ₹1000 × 8 × 1/100

₹8

The Intereset at the end of 2nd year = ₹1000 × 8 × 2/100

₹160

The Intereset at the end of 3rd year = ₹1000 × 8 × 3/100

₹240

Now we can obtain the interest of 4th year , 5th year , 6th year and so on ..

So ,

• Interest of 1st year = ₹80
• Interest of 2nd year = ₹160
• Interest of 3rd year = ₹240 ...

It is an AP as the difference between the consecutive terms in the list is 80 ... So, a = 80

As given that : We have to find the interest at the end of 30 years ,we shall find , a_30

So ,

a_30 = a + (30-1) d = 80 + 29 × 80

2400

Therefore , the interest at the end of the 30 years will be ₹2400