# A sum of Rs.1000 is invested at 8% simple interest per annum. Calculate the interest at the end of 1, 2, 3, ……. Years. If the sequences of interests an AP? Find the interest at the end of 30 years.

2
by dita

2015-03-13T19:19:46+05:30
Simple Interest = P × R × T ÷ 100

So S.I in first yr. ⇒ P x R x T / 100
⇒ 1000 x 1 x 8  ÷ 100
⇒ 80

In second Yr. ⇒ 1000 x 2 x 8 ÷ 100
⇒ 160
Similarly in third Yr. ⇒ 240

So , we get the A.P. like this i.e. 80, 160, 240

Therefor  a= 80 , d= 80.

we have to find out the interest at the end of 30 yr.
⇒ a = a + ( n-1 ) d

⇒ 80 + ( 30 - 1 ) 80
⇒ 80 + 29 × 80
⇒ 2400

There fore , the Interest at the end of 30 yrs is 2400
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2015-03-13T19:31:18+05:30
Given,
principal=1000
rate of interest=8%
number of years=1 year
SI=Pnr/100=1000x1x8/100=rs.80
when n=2 years,SI=1000x2x8/100=rs.160
when n=3years,SI=1000x3x8/100=rs.240
the sequence is
80,160,240,..........
this is in AP as a,first term=80,d,common difference=80
interest at the end of 30 years,t30=a+(n-1)d
=80+(30-1)80
=80+29(80)
=80+2320
=2400
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