Question

A contain sum at simple interest becomes ₹1200 in 2 years and ₹1400 in 4 years. Find the principal and interest percent per annum

Answer 1

Answer:

Principal = Rs. 1000

Rate of interest = 10%

Step-by-step explanation:

Formula used:

Simple interest formula:

simple interest for 'n' years

$=\frac{P\:n\:r}{100}$

As per given data

$1200=P+\frac{2\:P\:r}{100}$........(1)

$1400=P+\frac{4\:P\:r}{100}$........(2)

(2) - (1)

$1400-1200=(P-P)+\frac{4\:P\:r}{100}-\frac{2\:P\:r}{100}$

$200=\frac{2\:P\:r}{100}$

$100=\frac{P\:r}{100}$

$Pr=10000$

Now (1) becomes

$1200=P+\frac{2(10000)}{100}$

$1200=P+2(100)$

$1200-200=P$

$P=1000$

Put P=1000 in (1)

$1200=1000+\frac{2(1000)r}{100}$

$200=20\:r$

$r=\frac{200}{20}$

$r=10$