Question

find the sum and the rate of simple interest if it amounts to rupees 7200 in 5 years and to Rs 8064 in 8 years ​

Answer 1

Answer:

Let the sum be P

Let the rate of simple interest be r per annum

t1=5

A1=7200

P+Prt1/100=A1=7200

P(1+r×5/100)=7200

P((100+5r)/100)=7200....(i)

t2=8

A2=8064

P+Prt2/100=A2=8064

P(1+r×8/100)=8064

P((100+8r)/100)=8064....(ii)

Dividing (ii) by (i),

(100+8r)/(100+5r)=8064/7200

=28/25

2500+25×8r=2800+28×5r

2500+200r=2800+140r

60r=300

r=5% per annum

Putting value of r in equation (i),

P((100+5×5)/100)=7200

P×125/100=7200

P=7200×4/5

P=Rs 5760

Answer 2

Answer:

The principal is  6624 Rs and rate is 4.34%.

Step-by-step explanation:

Since, we know that the amount 7200 Rs is reached to 8064 Rs in 3 years.

It means that;

S.I for 3 years = (8064 - 7200) = 864 Rupees

So,    S.I. for 1 year = = 288 Rs.

      S.I. for 5 years =  = 1440 Rs

Now, we can find out the principal as;

Principal = 8064 - 1440 = 6624 Rs

Thus, we can find out the rate as,

             r = 4.34%

Thus, the principal is  6624 Rs and rate is 4.34%.