Question

nitesh borrows a sum.of rs 1200 at the beginning of the year. after 4 months rs 1800 more is borrowed at a rate of interest double the previous one. at the end of the year,the sum of interest on both the loans is rs 216. find the rate of interest per annum

Answer 1

let interest=x
1200*x*1/100=12x. [I=PTR/100]
1800*2x*1=24x

now,. 12x +24x=216
or,36x=216
or,x=6

Answer 2

given that first loan =p1= 1200

for 1 year rate of interest r

Implies

T=1 year.

then after 4 months,

second loan

p2=1800 also for one year

that is, 12-4=8 months.

Implies T=8/12=2/3 year

$interest=( \frac{1200 \times r \times 1}{100} ) + ( \frac{1800 \times 2r \times \frac{2}{3} }{100} ) = 216 \\ implies \\ 12r + 24r = 216 \\ that \: is \\ 36r = 216 \\ r = \frac{216}{36} therefore \: r = 6\%.$

Definition:

simple interest

$\frac{p \times n \times r}{100}$

where, p is principle amount

r=rate of interest per annum

n=no of years.#SPJ2.