Question

Find the sum and the rate of simple interest, if it amounts to 7,200 in 5 years and to 8,064 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

Step-by-step explanation:

Answer 2

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+rx5/100)=7200

P/(100+5r)/100)=7200....1)

t2=8

A2=8064

P+Prt2/100=A2=8064

P(1+rx8/100)=8064

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

Dividing (ii) by (o),

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

=28/25

2500+25x8r=2800+28x5r

2500+200r=2800+140r

60r=300

r=5% per annum

Putting value of r in equation (i),

P((100+5x5)/100)=7200

Px125/100=7200

P=7200x4/5

P=Rs 5760